






STATE SERIES 





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COPYRIGHT DEPOSIT. 



CALIFORNIA STATE SERIES SCHOOL TEXT-BOOKS 



PHYSIOLOGY AND HYGIENE 



COMPILED BY THE 

STATE TEXT-BOOK COMMITTEE 

AND APPROVED BY THE 

STATE BOARD OF EDUCATION 



o^o 



SACRAMENTO 
W. W, SHANNON, Superintendent State Printing 



LIBRARY of CONGRESS 
Two Conies Received 

AUG 17 »906 

CL«S *L Wc. No. 



■ C7 
/lot* 



Copyright, 1906, by 
THE PEOPLE OF THE STATE OF CALIFORNIA 

Copyright, 1902, by 
BUEL P. COLTON 



In the compilation of this book certain matter from an Elementary 
Physiology and Hygiene by Buel P. Colton has been used. All such 
matter is protected by the copyright entries noted above. 



PREFACE. 

In preparing this work for younger students especial 
pains have been taken to make it clear and simple. Sen- 
tences, paragraphs, and chapters have been made short, 
and a concise summary follows each chapter. So far as 
possible technical terms have been avoided and English 
words preferred to Latin, for instance, post-caval vein 
instead of vena cava inferior, spinal bulb instead of medulla 
oblongata, etc. The Latin form of the plural puzzles the 
student who has not had Latin ; hence the English form 
of the plural is used, as plenras, ganglions, ciliums, vil- 
luses, papillas, etc. 

The illustrations are made clear and distinct, and are 
labeled directly ; that is, the detail labels are on, or very 
close to, the part labeled, so that time and effort are 
not needed to associate the thing and the name. A large 
number of the illustrations are original. 

A few simple experiments are given ; for although much 
less can be done than with older students, yet considerable 
must be done if the subject is to be made clear. 

The subject of hygiene has received careful attention; 
for it must not be forgotten that the main object of this 
study is that each pupil may learn how to take better care 
of his own body. It has been the aim not to give mere 
arbitrary rules of health, to be blindly and implicitly fol- 
lowed, but to base all precepts of hygiene on the general 
principles of physiology, so that the pupil may understand 



IV 



Preface. 



the why and the how so far as possible. His obedience 
will be more ready and more complete when based on 
intelligence than when it is simply a submission to a 
peremptory command. In many cases, too, the general 
principle will serve as a guide where no rule has been laid 
down ; no treatise can cover all possible contingencies. 

At the end of the book is a glossary in which all tech- 
nical terms are pronounced and explained. 



CONTENTS. 



CHAFTER FAGE 

I. Introduction I 

II. The Bones . 5 

III. Muscles and Motion ....... c 16 

IV. The Muscles and the Bones ....... 28 

V. The Nervous System — Sensation and Motion 36 

VI. Circulation of the Blood ....... 47 

VII. Control of Circulation .....,., 67 

VIII. The Blood and the Lymph 74 

IX. External Respiration ........ 83 

X. Internal Respiration ... . . . 97 

XI. Ventilation and Heating ....... 106 

XII. Dust and Bacteria . . . . . - . .114 

XIII. Excretion 123 

XIV. Foods and Cooking 134 

XV. The Digestive System — Digestion in the Mouth . . . 146 

XVI. Digestion in the Stomach . . . . . . 156 

XVII. Digestion in the Intestine . . . . . . .164 

XVIII. Absorption . . , . . . , . . .172 

XIX. Hygiene of Digestion — Nutrition ..... 181 

XX. Exercise and Bathing . . . . . . . .192 

XXI. The Brain 198 

XXII. The Senses — The General Senses — Touch and Temperature 

Sense 208 

XXIII. The Sense of Sight 215 

XXIV. Defects of Eyesight and Care of the Eyes . . . .223 
XXV. Taste, Smell, Hearing, and the Voice 233 

XXVI. Accidents — What to do till the Doctor comes . , . 240 

XXVII. Vaccination 250 

XXVIII. Stimulants and Narcotics 253 

Glossary 261 

Index ..,,.... 273 

v 



TO THE TEACHER. 

It is not the fault of the teacher that the human body is very com- 
plex in structure and that many of the functions are obscure. Never- 
theless the teacher is responsible for making the subject as clear as is 
possible. To do this it is absolutely essential to perform some experi- 
ments and to show some of the internal organs of such an animal as 
the rabbit, or materials obtained from the butcher. This involves 
work, and sometimes work that is not altogether pleasant. But no 
earnest teacher will shrink from work simply because it is not agreeable. 

Every school should have a microscope, by means of which to show 
the corpuscles of the blood, cells from various tissues, the circulation 
of blood in a frog's web, or in the gills of a tadpole. From various 
dealers in school supplies there can be purchased mounted slides illus- 
trating most of the kinds of cells and tissues of the body. These can 
be successfully used by teachers who have not had the advantages of a 
thorough training in histology. 

When studying the bones the teacher can usually borrow some 
human bones from the nearest physician. Also get a femur of a horse 
or cow and saw it in two lengthwise. It will show the structure as 
well as a human femur. It is easy to test the composition of bone by 
burning and by acid. Corned beef shows well the structure of muscle. 
A sheep shank from the butcher may be used to show the joints, 
synovia, cartilage, ligaments, etc. Most pupils will be ready to help 
dissect a heart and will be delighted to see the action of the valves. 

By means of a common bulb syringe and a little glass and rubber 
tubing the action of the arteries and the nature of the pulse and capil- 
lary flow may be illustrated." The circulation of blood in the web of a 
frog's foot is such an interesting and instructive sight that the teacher 
should show it to the class without fail. Even if the school has no 
microscope and the teacher without experience, it is often possible to 
get a near-by physician to show it to the class. The coagulation of the 
blood is readily shown. The experiments illustrating the action of the 



viii To the Teacher. 

diaphragm are very helpful, and any teacher possessing a modicum of 
ingenuity and willingness to work can prepare them. In addition to 
the experiments given in illustration of the chemistry of respiration, it 
is desirable to show nitrogen and the composition of the air. This can 
readily be accomplished by following the directions in the larger book 
or in any chemistry. 

To learn the temperature of the body borrow a clinical thermometer 
from a physician. Have the children make little paper windmills to 
show the air currents in rooms, over stoves, registers, radiators, etc. 
The children should test the currents of air at all gratings and registers 
in the schoolroom by holding a handkerchief up close to them. The 
teacher should place a board under a window (as directed in this book) 
to show how to ventilate a room without unpleasant drafts. Each 
pupil should prepare a section of tooth as directed in this book. When 
studying the subject of absorption, the teacher should get from the 
butcher about a foot of the small intestine of a calf. He will wash it 
clean for a small consideration. Cut this into pieces an inch long. 
Turn them inside out and place them in shallow dishes of water. The 
villuses will readily be seen. A piece of the gullet will show the mus- 
cular and mucous coats. Have the pupils make a careful study of 
Fig. 87 and also of Figs. 85 and 86, which are designed to lead up to 
Fig. 87. If the teacher is willing to practice, he can soon learn to 
demonstrate muscle action by means of frog^ muscle and to show 
reflex action of the spinal cord with a -frog. 

Many interesting experiments on the senses can be made with chil- 
dren, such as the test of touch with compass points, keenness of sight, 
hearing, accuracy of the muscular sense, etc. The internal structure 
of the eye never fails to awake enthusiasm, and the teacher should 
show this, and perhaps some of the pupils can also succeed in doing 
the same. If the teacher can obtain a book on nursing, or, better still, 
persuade a physician or trained nurse to come before the class, they 
can learn how to prepare and apply bandages, to dress wounds, to treat 
for drowning, etc. 



ELEMENTARY PHYSIOLOGY. 

CHAPTER I. 

INTRODUCTION. 

The Care of a Machine. — In order to take good care of 
a machine one must know about its different parts, what 
each part is to do, and the relation of the parts to one 
another. He must keep the machine clean and well oiled, 
and must not overwork it. Otherwise it will neither do 
good work nor last long. This is true not only of machines 
like typewriters and sewing-machines, but of bicycles, and 
even of such simple tools as knives and scissors. We 
would not trust the management of any valuable machine 
to one who did not know enough to take good care of it. 

The Care of the Body. — The care of the body is of vastly 
greater importance. We can get new parts to replace 
those worn out in a machine. While we can get artificial 
limbs, we cannot replace such organs as an eye, the heart, 
or the lungs. If we do not take good care of our bodies, 
we cannot keep well, live long, or do good work. So we 
need to know about the different parts of our bodies, the 
work that each is to do, and the relation of the parts to 
each other. 

This knowledge is desirable for everybody ; but espe- 
cially necessary for those who live a quiet, indoor life. In- 
door people do not get as much exercise or as much fresh 

i 



2 Physiology. 

air as those who live outdoors. An indoor life is always 
more or less artificial, and we need to take especial care 
that our bodies do not suffer. It is believed that one 
seventh of the deaths among civilized races are due to lung 
troubles. Those who live outdoors have little trouble of 
such kind. We need to learn about the air and breathing, 
about exercise and bathing, about food and digestion, about 
blood and its circulation, about the nervous system, etc. 

Hygiene. — Hygiene is the art of preserving the health. 
This is the main object of our study of this subject. 

Physiology. — Physiology is the science of the action of 
the body and its various parts. We must know the natural 
action of the parts of the body to be able to keep them in 
good working order. 

Organ. — An organ is any part of the body that has a 
special work to do, as the hand, eye, or heart. 

Function. — The work or action of an organ is its 
function. 

Anatomy. — Anatomy is the science of structure. We 
need to know something of the structure of our bodies. 
For this purpose we may study the internal structure of 
the sheep, pig, calf, and rabbit — which is very similar to 
our own. We can take the hearts, lungs, brains, eyes, and 
muscles of such animals to learn something of the struc- 
ture of these organs in our own bodies ; if we fail to do this, 
we can never get a clear understanding of the subject. 

Tissues. — Every organ is made up of several different " 
kinds of material. For instance, in a slice across a ham 
we see skin on the outside, then fat meat, lean meat, and 
bone. These " primary building materials" of the body 




Introduction. j 

are called tissues. A tissue is a collection of similar cells 
devoted to the same work ; or, in other words, a tissue 
is a set of cells having the same structure and the same 
function. Thus we have muscular tissue, nervous tissue, 
bony tissue, etc. 

Cells. — The whole body is made up of small parts, called 
cellsy which are to be compared to the bricks in a house. 
These cells are of various shapes in the different tissues. 
The living material of the body is called protoplasm. It is 
a jelly-like substance resembling the 
white of an egg, though often pre- 
senting a dotted appearance. A cell, 
in its simplest form, is merely a dis- 
tinct particle of protoplasm. Each 
cell usually has, however, a more Fig. 1. Epithelial ceils from 

. . nii 7 the Inside of the Cheek. 

dense central part, called the nucleus. 

The great majority of cells have a distinct covering or 
cell-wall. A grape or cherry serves very well to illustrate 
a cell. The skin represents the cell-wall, the pulp corre- 
sponds to the protoplasm, and the seed to the nucleus. 
(See Fig. 39, Cells of the Epidermis.) 

Division of Labor in a Community. — We are all aware 
of the advantages of division of labor in a community. If 
each person learns to do one thing well, all can work 
together economically for the common good, time is saved, 
and cheaper and better goods are produced. 

Division of Labor in the Body. — In the body there is a 
division of labor similar to that in a community. In the 
first place each organ has its special work, and the various 
organs act helpfully together, each working for all the rest 
and worked for by them. 



4 Physiology, 

The general structure of all the cells is about the same, 
yet they differ enough for us to tell them apart. They 
differ more in their work than in their appearance. Each 
has some one kind of work that it can do well, and to 
which it devotes itself. The nerve cells receive impressions 
from the outer world, carry nerve currents, and control the 
various actions of the body. The muscle cells have as 
their work the production of motion. 

The Life of Cells. — Each cell must take food for itself 
and grow. Each has a birth, life, and death, as each indi- 
vidual in a community of men ; and as the community 
continues, while the individual members are constantly 
changing, so, in the body, while the form remains about 
the same from year to year (in the adult), the cells are 
continually changing, some dying, and others taking their 
places. Thus it is seen that though the cells are packed 
closely together and though they work in groups, each cell 
leads, in one sense, an independent life. Like the indi- 
vidual in the community, each lives for itself, yet all work 
together for the common good. 



CHAPTER II. 

THE BONES. 

The Two Parts of a Skeleton. — The skeleton consists of 
two portions, (i) the central axis, or spinal column, to 
which the head belongs; and (2) the limbs and the bones 
belonging to them. 

The Uses of the Bones. — 1. The skeleton gives the form 
to the body. 

2. It supports the softer tissues. 

3. It protects softer parts, as the brain in the skull, the 
spinal cord in the spinal column, the heart and lungs in 
the chest, etc. 

4. The bones serve as levers in producing motion and 
locomotion. 

Study of a Vertebra. — Take a vertebra from the middle of the spinal 
column : — 

1. Its most solid part is its body. 

2. On the dorsal side of this is the neural arch, forming with the 
body the neural ring, through which the spinal cord passes. 

3. From this arch there extend projections, or processes. Hold the 
vertebra by the tip of its longest process, and place it beside the cor- 
responding vertebra in the complete skeleton. Note that : — 

(a) The body is flattened where it fits against the vertebras above 
and below it ; 

(b) The holes in the vertebras form a passage for the spinal cord ; 

(c) The middle projection is the spinous process, and the series of 
spinous processes form the ridge of the backbone ; 

(d) The two side projections are the transverse processes. 

5 



Physiology. 



Fit together two vertebras in their proper order and observe that : — 
(e) The openings at the sides, through which the spinal nerves pass, 
are iormed by notches, or grooves, in the two vertebras. 



Neural Arch 



Body 




Transverse Process 



Spinous Process 



Neural Ring 
Fig". 2. Upper View of Thoracic Vertebra. 



Demi-facet for Head of Rib 



Body 




Anterior Articular 
Process 



Facet for Tubercle ot 
Rib 



Transverse Process 



..Spinous Process 



Fig. 3. Left Side View of Thoracic Vertebra. 

(/) The two projections extending upward from the ring of one 
vertebra fit against two projections extending downward from the other 
vertebra. These are the anterior and posterior articular processes. 



The Spinal Column. — The central part of the skeleton 
is the backbone, or spinal column, As a whole it is a 



The Bones. 



column, widening toward the base, composed of a series of 
separate bones called vertebras. 

Each vertebra has seven projections, four for joining 
other vertebras (two upper and two lower), two side, and 
one spinous. 



Hole for Blood Tubes 



Body 




Anterior Articular Facet 

Neural Arch 



Spinous Process 



^•...Neural Ring 



Fig. 4. Upper View of Cervical Vertebra. 



Body 




Spinous Process 



Fig. 5. Left Side View of Cervical Vertebra. 

How the Vertebras Fit Together. — The smooth places 
where the projections join are called facets. Observe on 
each side of the body of the vertebra a facet where the 
head of the rib joined it. There is also a facet on the side 
process where the side of the rib joined it. 

The Cervical Vertebras. — The seven cervical (neck) 
vertebras have holes through their side projections for the 
passage of blood tubes. 



8 



Physiology. 



f LAT BONES OF THE SKULL. 



NASAL BONES -"Oil 



-THE CRANIUM, 

-MALAR (CHEEK) BONE. 
■SUPERIOR MAXILLARY BONES 
INFERIOR MAXILLARY BONE 
"SPINAL COLUMN. CERVICAL REGION* 
^CLAVICLE (COLLAR BONE) 



SHOULDER BLADE — 




Fig. 6. Side View of the Human Skeleton, 



The Bones. 



9 



TABLE OF THE BONES. 



Head (28) 



Face (14) 



■ Ears (6) 



Cervical Region (8) 



Thorax (37, 



Upper Extremities (64) 



Lumbar Region (5) 
Pelvis (4) 



■ Skull (8) ■ 



Frontal (forehead). 

2 Temporal (temples). 

2 Parietal (side). 

Occipital (posterior base). 

Sphenoid (base). 

Ethmoid (base of nose and between eyes). 

r 2 Superior Maxillas (upper jaw). 

2 Nasal (bridge of nose). 

2 Malar (cheek). 

2 Lachrymal (inner front corner of orbit). 

2 Turbinated (within nostrils). 

2 Palate (posterior hard palate). 

Vomer (nasal partition). 
[ Inferior Maxilla (lower jaw) e 

{ Malleus (hammer). 
{ Stapes (stirrup). 
I Incus (anvil). 

7 Cervical Vertebras (neck). 
Hyoid Bone (base of tongue). 

14 True, 6 False, 4 Floating Ribs. 
12 Thoracic Vertebras (back). 
Sternum. 



{Clavicle (collar-bone). 
Scapula (shoulder-blade). 
Humerus (arm). 
Radius 1 rc N 

Ulna } (fore-arm). 

8 Carpal (wrist). 

5 Metacarpal (palm). 

14 Phalanges (fingers). 

5 Lumbar Vertebras (loins). 



Shoulder. 



Arm. 



Hand. 



{2 Innominates. 
Sacrum. 
Coccyx. 



Lower Extremities (60) 



Thigh. 
Leg. 

Foot. 



Femur. 
f Patella (knee-pan). 
\ Tibia (large bone). 
I Fibula (outer bone). 

7 Tarsal (instep, heel). 

5 Metatarsal (arch). 

14 Phalanges (toes). 



2 — PHY 



io Physiology. 

Atlas and Axis. — The first vertebra, the atlas, has no 
body. The second vertebra is the axis. It has a peg 
which runs up into the atlas. In shaking the head, the 
atlas, with the head, turns on this peg of the axis. In 
nodding the head, the head simply rocks back and forth 
on the atlas. 

The Thoracic Vertebras. — The twelve rib-supporting 
vertebras are the thoracic vertebras. 

The Lumbar Vertebras. — The next five are the lumbar. 

The Sacrum and Coccyx. — The sacrum is composed of 
five vertebras grown together, and the remaining four are 
combined in the coccyx. 

Review of the Spinal Column. — Let the eye slowly re- 
view the whole spinal column, noting in what points the 
vertebras are all alike. Note also their differences. 

Flexibility of the Spinal Column. — In well-prepared 
skeletons there are pads of felt which take the place of the 
layers of cartilage that were between the vertebras. These 
cartilages are tough and elastic, and firmly attached to the 
vertebras above and below. They serve both to keep the 
vertebras apart and to hold them together. When we bend 
the shoulders to the right, the right edges of these carti- 
lages are compressed, and the left edges are stretched, as 
a piece of india rubber would be if it were glued be- 
tween the ends of two spools, and the whole were slightly 
bent. The cartilages also, by their elasticity, protect 
the brain from the shock it would receive in jumping, 
walking, etc. 

Curves of the Spinal Column. — View the spinal column 
from the side. Draw a line representing all its curves. 



The Bones. 



II 



The Cavities of the Skeleton. — Examine the cavity of the skull. If 
the class has not a skull which has been sawed across, look into the 
skull cavity through the hole where the spinal cord joined the brain. 



Neural Arch 



Body 



f Transverse Process 




Neural Ring 
Fig. 7. Upper View of Lumbar Vertebra. 



Body 




Spinous 
Process 



Posterior Articular Process 
Fig. 8. Side View of Lumbar Vertebra. 

Observe the conical shape of the chest. In the entire body the 
bones and muscles about the shoulders usually make a reversed cone of 
the upper part of the trunk. 

Observe that most of the ribs are connected with the breastbone by 
cartilages. 

The upper limbs are jointed with the bodv only where the inner 
ends of the collar bones join the breastbone. 



1 2 Physiology. 

The Skeleton of a Cat or Rabbit. — Examine the skeleton of a cat or 
rabbit for the sake of comparison. Note especially the skull and spinal 
column. This knowledge will aid in understanding the brain and 
spinal cord. 

The Weight of Bones. — The bones make about one sixth 
of the weight of the living body. When dried they may 
lose half of their weight. 

Microscopic Structure of Bone, i . Examine with a Hand Lens. — 

Hold a mounted cross-section of bone up to the light and examine with 
a hand lens. The solid part of the bone will be seen to be pierced by 
many small holes (or if the holes are filled, they will appear as black 
spots). These are the cross-sections of the canals, through which run 
the blood tubes, mainly lengthwise, through the bone. 

2. Examine with the Low Power of a Compound Microscope. — 

Examine the section under the microscope, using a half-inch objective. 
The bony matter will now be seen to be arranged in rings around the 
canals, somewhat like the rings seen on the end of a log. 

Between the rings are circles of elongated dark dots. These are 
cavities in which were the live bone-corpuscles which built up the bone. 
The bone was at first cartilage. Later, mineral matter was deposited, 
forming true bone. 

3. Examine with a High Power. — Now examine the section under a 
one-fifth-inch objective. From the dark cavities there run out, in every 
direction, little crevices, appearing as fine black lines. Through the 
haversian canals, lacunas, and crevices, the nourishing materials of the 
blood reach all parts of the bone. 

The Chemical Composition of Bone. — 1. Take a tall, narrow jar, or 
a lamp chimney corked at one end, and nearly fill with water. Add 
one sixth as much hydrochloric acid. Put into this a slender, dry bone, 
such as a fibula or rib. In twenty-four hours take it out, rinse it thor- 
oughly, and examine it. The acid will probably have dissolved out the 
mineral matter and left the animal matter so soft that it .may be tied 
into a knot. 

2. Lay a piece of bone on a shovel, or piece of sheet iron, and place 
in the fire. The animal matter is burned out, leaving the brittle min- 
eral matter* 



The Bones. 



*3 



Composition of Bone. — Bone is composed of two thirds 
mineral matter and one third animal matter; in childhood 
the animal matter is in larger proportion, while in old age 
the mineral matter is in excess. The mineral matter is 
chiefly phosphate of lime, while the animal matter is 
largely gelatin. 



Lamellas 



Lacunas 




^ms^m^k 



tm<& 



^mmm^Wk 



Canaliculi Haversian Canai 

Fig. 9. Cross-section of Bone. (Highly Magnified.) 



Classification of Joints. — i. Immovable, such as the 
joints between the bones of the skull ; 

2. Mixed, such as the joints between the vertebras; 

3. Movable, which allow free motion between the parts; 

(a) Ball and socket, as in the hip and shoulder ; 

(b) Hinge, as in the knee and elbow ; 

(c) Pivot, as in the forearm, and between the atlas and 
axis; 



14 Physiology. 

(d) Gliding, as between the short bones of the wrist 
and of the ankle. 

Study of Joints. — Examine these joints in the prepared skeleton, 
and so far as possible, in sheep shanks, or in fresh specimens of rabbits. 
Compare the ball and socket joints of the hip and shoulder. Also com- 
pare the hinge joints of the knee and elbow. 

Hygiene of the Bones. — Sometimes the bones of chil- 
dren are lacking in mineral matter, and are too soft and 
flexible. This is true in a disease called rickets. Even if 
the bones are natural, children should not be encouraged 
to walk early, as bow-legs may result. Most bow-legged 
persons seem to be active, and probably their muscles 
developed faster than the bones. Unnatural positions or 
over-use of special groups of muscles may result in lateral 
curvature of the spine. The height of seats and desks 
should be carefully looked after. 

Sprains and Dislocations. — Sprains and dislocations are 
injuries to the joints, and often bring more serious results 
than a broken bone. There should, usually, be complete 
rest until the part can be used without pain. Otherwise a 
stiffened joint may result. Hot water applied to a sprain 
or bruise with rubbing will reduce soreness and may pre- 
vent discoloration. But if there is inflammation, cold water 
should be applied. Bandages may be needed for support. 

Broken Bones. — When a bone is broken, of course a 
physician should be sent for. Care must be taken that the 
limb be kept straight. If this is not done, the sharp ends 
of the bone (see Fig. 22) may cut or tear the surrounding 
tissues, or even cut blood tubes. So, if the person must 
be carried, it is well to tie a piece of board under the limb 
to keep from bending it. A cane, umbrella, or any light 
rigid bar will serve for this purpose. 



The Bones. i 5 

Summary. — i. The skeleton consists of the central axis and the 
limbs. 

2. Each vertebra consists of a body, ring (around spinal cord), and 
processes. 

3. Pads of cartilage connect the vertebras. 

4. Throughout the bone there are tubes and crevices through which 
it receives its nourishment from the blood. 

5. Bone consists of animal matter with limy matter embedded in it. 

6. Sprains should be treated carefully to avoid stiffened joints. 

Questions. — i. Why do the bones of old people break so much 
more easily than those of children ? 

2. What is the use of the central marrow ? 

3. What is the work of the red marrow in the spongy ends of the 
bones ? 

4. What are " sesamoid " bones ? 



CHAPTER III. 

MUSCLES AND MOTION. 

Motion and Life. — Motion is one of the surest signs of 
life. While we are sitting still, as we say, there are fre- 
quent slight motions of the head, body, and limbs. Even 
during sleep the movements of breathing may be seen; the 
hand laid upon the chest may feel the beating of the heart, 
and the finger detect the pulse in a number of places. We 
must move to get our food, or at least to eat and digest it. 
We often move to avoid injury. Motion is necessary for 
speech and in the use of the sense organs. How are all 
these motions produced? 

Experiments with the Muscles in our own Bodies. — i . Clasp the 
front of the right upper arm ; draw up the forearm strongly and as far 
as possible. Note the changes that are felt in the biceps muscle. 




Fig. 10. The Shortening and Thickening of the Biceps Muscle in raising the Forearm 

2. Repeat the experiment, and with the thumb and finger feel the 
cord, or tendon, at the lower end of the muscle, just within the angle of 
the elbow. 

i6 



Muscles and Motion. 17 

3. Span the muscle, placing the tips of the fingers in the angle of the 
elbow, and the tip of the thumb as far as you can up the arm ; again 
bend the arm. What change in the muscle does this show ? Any 
muscle that bends a limb, as does the biceps, is called a flexor muscle. 

4. Clasp the back of the upper right arm ; forcibly straighten the 
arm. The muscle lying along the back of the arm is the triceps muscle. 
It is called an extensor muscle because it extends, or straightens, the arm. 

5. Clasp the upper side of the right forearm near the elbow ; clench 
the right hand quickly and forcibly ; repeat rapidly. 

6. Notice the mass of muscle at the base of the thumb ; pinch the 
forefinger and thumb strongly together. What changes can be seen and 
felt? 

7. Place the hand on the outside of the shoulder ; raise the arm to 
the horizontal position ; repeat with a weight in the hand. 

8. Stand erect with the heels close to each other, but not quite 
touching ; let the arms hang freely by the sides ; rise on tiptoes, with- 
out moving otherwise ; repeat ten times. 

9. Place the tips of the fingers on the angles of the lower jaw ; shut 
the teeth firmly, and note the bulging of the masseter muscle. 

10. Press the fingers on the temples ; again shut the jaws firmly, and 
feel the action of the temporal muscles. 

By these experiments we learn that when a muscle works 
it becomes shorter, thicker, and harder. 

The Action of Muscle. — The action of muscle is always 
a " pull." The muscle shortens, at the same time thicken- 
ing and hardening. It must be kept clearly in mind that 
the work of the muscle is done by its shortening and not 
by either the hardening or thickening. But the hardening 
and thickening are often more noticeable than the shorten- 
ing, and by means of them we may locate the muscle that 
is producing any motion. 

Action of Frog's Muscle. — The action of muscle may be seen much 
more clearly in a frog's calf muscle, as shown in Fig. 1 1 . When the 
nerve is stimulated at " A " a nerve impulse runs along the nerve to the 
muscle and makes it shorten and widen, raising the weight as shown in 
the right half of the figure. 



i8 



Physiology. 




SHORTENED 



ELONGATED 

Fig. 1 1 . Action of the Calf Muscle of the Frog, showing the Relations of the 
Sciatic Nerve. 

Structure of Muscle. — Chipped beef shows well the 
structure of muscle. The white network is connective 

tissue. Its work is to hold 
0r,gm the parts of the muscle to- 

Bundie of Muscle Fibers gether and to support the 
muscle as a whole. In the 
meshes of the white network 
is the red muscle tissue. The 
partitions which run all 
through the muscle are con- 
tinuous with the muscle 
sheath, and both are con- 
tinuous with the tendons at 
the ends of the muscle. In 
fresh muscle the sheath and 
the partitions are transpar- 
ent, and are not very easily 
noticed. When meat is cooked or salted the connective 
tissue becomes white and opaque. 





Muscle Sheath \ 

CROSS SECTION 



Tendon 



nsertion 



LONGITUDINAL SECTION 

Fig. 12. The Structure of Muscle. 



Muscles and Motion. 



*9 



Microscopic Structure of Muscle. — If a tiny shred of 
muscle, such as you may remove from the teeth with a 
toothpick, be put in a drop of 
slightly salted water and exam- 
ined under a good microscope, the 
fibers may be seen. These are 
small thread-like bodies, with cross 
markings, from which they are 
called striated or striped muscle 
fibers. From the fact that they 
are under the control of the will 
they are called voluntary muscle 
fibers. Not all striated muscle 
fibers are voluntary. The heart 
muscle fibers are in a special class, being striated but 
involuntary. The muscles connected with the bones 
are called skeletal muscles. They are all striated and 
all voluntary. 




Fig. 13. Two Striated Muscle 
Fibers showing the termina- 
tions of the Nerves. 



Plain Muscle Fibers. 



Nucleus 



■"* Isolated Fibers 



Fibers Joined 



■In the walls of the arteries, of 
the gullet, the stomach, the in- 
testines, the bladder, and else- 
where, there are muscle fibers 
of a different kind from those of 
the skeleton. These fibers are 
spindle-shaped cells, as shown in 
Fig. 14, with a nucleus near the 
center, and do not have the cross- 
markings. Hence they are called 
plain, smooth, or un-striated mus- 
cle fibers. Owing to the fact 
that they are not under the con- 
trol of the will they are called involuntary muscle fibers. 




Fig. 14. Plain <unstriated) Muscle 
Fibers. 



20 



Physiology. 




The involuntary muscle fibers are usually much slower in 
their action than the voluntary fibers. 

Heart Muscle Fiber. — The 

fibers which make up heart 
muscle are different in appear- 
ance from either the striated or 
the smooth muscle fibers. They 
are more or less branched, as 
shown in Fig. 15. No sheath 
has been found on these fibers. 

A Muscle Fiber is a Cell. — 

It is easily seen that each plain 
muscle fiber is a single cell, hav- 
ing its distinct nucleus. The 
Fig. 15. Muscle Fibers from the Heart, same is true of the heart muscle 

magnified, showing their cross striae, fib t h Ugh they are not SO 

divisions, and junctions. ' o J 

The nuclei and cell-junctions are shown simple, being more Or leSS 

only on the right hand side of the 

figure. branched. 

Effect of Cooking Muscle. — In well-cooked corned beef 
the connective tissue is thoroughly softened, and the mus- 
cle fibers are easily separated. Thorough cooking, espe- 
cially stewing, will soften the connective tissue, and may 
make tender meat that, cooked otherwise, would be very 
tough on account of the large amount of connective tissue. 

Imitation of Structure of Muscle. — Take a number of pieces of red 
cord to represent the muscle fibers. Wrap each in white tissue paper; 
this represents a single fiber sheath. Lay a number of these side by 
side, and wrap them all in a common sheath. Let the tissue paper pro- 
ject beyond the ends of the threads, and here compress it into a com- 
pact cylinder ; this last represents the tendon. 

Connective Tissue the Skeleton of Muscle. — If all the 

muscle fibers were removed from a muscle, the sheaths 



Muscles and Motion,, 21 

and partitions would remain, and show the form of the 
muscle just as the partitions remain in a squeezed orange 
or lemon. The connective tissue forms a framework for 
all the soft tissues of the body, and if their working cells 
were removed, the connective tissue would remain, and 
show, more or less completely, the form of the part. Con- 
nective tissue may be called, therefore, the skeleton of the 
soft tissues. Muscle consists, then, of soft transparent 
tubes, filled with a semi-fluid muscle substance. By scrap- 
ing the surface of a steak the muscle substance may be 
obtained, leaving the connective tissue. This is a good 
way to get the nutritious part of beef for an invalid. 

Importance of Muscles. — The muscles make up nearly 
half the weight of the body. This fact of itself should 
lead us to conclude that the muscles are of great impor- 
tance. Muscles are used in nearly every action of the 
body, not only in locomotion, but in respiration, circulation, 
digestion, speech, etc. It is very necessary that at the 
beginning we understand their action. 

Duration of Muscle Shortening. — A muscle cannot be 
kept shortened for any great length of time. If one holds 
the arm out horizontally as long as he can, he soon feels 
fatigue, later pain, and he is likely to feel a soreness in the 
muscle for several days afterward. The law of muscle 
action is to alternate periods of rest with periods of action. 
In many exercises, as in walking, the limbs act alternately, 
one resting or recovering while the other works. 

Alternate Action of Flexors and Extensors. — When the 
biceps muscle shortens and bends the arm, the triceps 
lengthens (see Fig. 16). When the triceps shortens, as in 
straightening the arm, the biceps lengthens. If the biceps 
and triceps both shorten at the same time, and with equal 



22 



Physiology, 



Deltoid 



Serratus Magnus 



Rectus Femoris 



Tibialis Anticus 




Fig. 16. Front View of the Superficial Muscles 



Muscles and Motion. 



*3 



Extensors of the Hand 



Triceps 



Latissimus Dorsi 



Gluteus Maximus 



Vastus Externus 



Flexors of the Foot 



Trapezius 




Deltoid 



Flexors of the Hand 



Biceps Cruris 



Gastrocnemius 



Tendo Achillis 



Fig. 17- Back View of the Superficial Muscles. 



24 Physiology. 

force, no motion will be produced. Sometimes this is done 
on purpose, as when, in wrestling " square-hold," one holds 
the arm rigidly bent at a right angle, to keep his opponent 
from either pushing or pulling him. In the body are many 
flexors and extensors " paired off"; they act alternately, 
like the biceps and triceps in the arm. 

Symmetrical Development of the Muscles. — The muscles 
of the two sides of the body are the same in number and 
arrangement. At birth they are probably about equal in 
size, weight, and strength. Most persons early become 
right-handed, and the greater use of the right hand and 
shoulder makes the muscles of this side larger and heavier. 
The muscles pulling on the bones slightly modify them in 
shape. The whole body may become noticeably one-sided. 
Most persons step harder on one foot than on the other, as 
shown by the sound of the footstep, or by the constant 
wearing of one shoe sole or heel faster than the other. In 
many persons one shoulder is carried higher than the 
other. 

To Overcome One-sidedness. — Symmetrical development 
should be carefully sought, and any tendency to a one- 
sided development should, so far as possible, be avoided. 
We should use the left hand more. There are many ad- 
vantages in being able to use either hand. In carving, in 
shaving, in bandaging, in giving medicine, it may be neces- 
sary to use the left hand skillfully. The pianist and the 
harpist use the two hands about equally, while the violinist 
puts much more skill into his left hand. Trainers of 
athletes often begin by developing the left side of the 
body till it equals the right in size and strength. 

Muscles the Source of Strength. — Our strength depends 
on our muscles. It is a fine thing to have strong, well- 



Muscles and Motion. 25 

developed muscles, not only because they give beauty of 
form, but because extra strength and endurance may be 
needed in case of accident, to save one's own life or that 
of others. In a case of fire the ability to climb, to go up 
or down a rope " hand over hand," may be all-important. 
Any one's life may depend on his ability to run far and 
swiftly, to swim, to jump, or to lift a heavy weight. 

The Number of Muscles. — There are over five hundred 
muscles in the human body. These vary in size from less 
than an inch in length, in the ear and in the larynx, to a 
foot and a half long in the thigh. 

The Arrangement of Muscles. — The muscles of the two 
sides of the body are paired, and naturally are about equal 
in size and strength. The muscles of the limbs are further 
paired into flexors, which bend, and the extensors, which 
straighten the limbs. The muscles are also arranged more 
or less in layers. There is generally an outer layer and a 
more deep-seated layer. 

Forms of Muscles. — Muscles are of various shapes. 
The prevailing form in the limbs is spindle-shaped, or 
fusiform. Some muscles are flat, some have their fibers 
arranged like the barbs of a feather, and are hence called 
penniform. Some muscles have a tendon in the middle 
which runs through a loop, as in the case of the muscle 
which depresses the lower jaw. Muscles which close open- 
ings are circular, and are called sphincter muscles. 

Peculiar Muscles. — The diaphragm is a sheet of muscle 
that forms a partition between the chest and the abdomen. 
It is arched, and has a clear tendinous center. The ab- 
dominal muscles form a wall to hold the organs of the 
abdominal cavity. These muscles also aid in breathing, 

3— PHY 



26 Physiology. 

especially in forced expiration, as after violent exercise and 
in coughing. The abdominal wall consists of several layers 
of muscle. 

Muscles of Expression. — The facial expression is due 
to the action of the muscles of the face, which in turn are 
under control of the cranial nerves. The habitual position 
becomes somewhat " fixed," so it is true that character is 
often shown by "the looks." Cultivation of happy thoughts 
therefore tends to make one better looking. 

Muscles and Fat. — Fat fills in space between muscles, 
and, if abundant, forms a layer over the muscles. One 
notable instance is the hollow triangular space between 
the muscles of the cheek. If there is very little fat, a 
depression is seen, forming the " hollow cheeks." But an 
abundance of fat makes a corresponding elevation. 

Convulsions. — These spasmodic actions are due to dis- 
ordered action of the muscles, and to a disturbed action 
of the nervous system that controls the muscles. Various 
disturbances, such as indigestion, may by reflex action 
bring on convulsions. 

Summary. — i. Motion is involved in nearly every action of the body. 

2. The action of muscle is a shortening, accompanied by a thicken- 
ing and hardening. 

3. Muscle consists of fibers with a connective tissue sheath for each 
fiber, bundle of fibers, and for the muscle as a whole. 

4. The skeletal muscle fibers are striated. 

5. The muscles make about half the body's weight. 

6. Muscles can remain shortened only a little while. 

7. The muscles should be developed symmetrically. 

8. There are about five hundred muscles in the body. 

9. The muscles of the two sides are alike. 

10. The muscles of the limbs are spindle-shaped. 

Questions. — 1. What effect is produced by carrying a heavy satchel 
for a long distance without resting? 



Muscles and Motion. 27 

2. Which is more tiresome, standing still or walking? Why? 

3. When the boy, who thinks he can strike a hard blow, says, 
" Feel my muscle," does he usually call attention to the muscle used in 
striking? 

4. Why are the sides of the body often sore after walking on icy 
pavements ? 



CHAPTER IV. 

THE MUSCLES AND THE BONES. 

Skeletal Muscles. — When we look at the skinned car- 
cass of an animal in the market, we observe that the mus- 
cles almost completely cover the bones. Those which are 
attached to the bones are called skeletal muscles. They 
act upon them as levers, making the motion strong, quick, 
and accurate. Without bones our motions would be like 
those of an earthworm or slug, slow and uncertain. The 
muscles, acting through the bones, can lift a weight that 
would crush the muscles if laid directly upon them, while 
a bone, able to support a heavy weight without being 
crushed, has no power in itself. The muscles have active 
strength, the bones have passive strength. 

Relation of the Muscles and the Bones. — Examine Figs. 
10, 1 6, and 17. For this work you should have the bones of 
an arm. Locate the biceps muscle in its relations to these 
bones as shown in the figures. Feel the biceps of your 
arm. Note that its thickest part is opposite the most 
slender part of the bone. But at the enlarged end of the 
bone the muscle has narrowed to a slender tendon which 
passes over the joint to be attached to the next bone, thus 
giving more slenderness, flexibility, and freedom of motion 
to the joint. Most of the skeletal muscles are attached to 
bones. There are some exceptions, such as the circular 
muscle which closes the mouth when the lips are pursed up. 

X-Rays and their Use, — By means of X-ray apparatus 

28 



The Muscles and the Bones. 



29 




Fig \t 



X-Ray Photograph of Hand showing Shot carried for " 
(From Recreation, by permission of G. O. Shields.) 



venty Years. 



the physician can photograph through the body and show 
the location of the bones. This process is useful in show- 
ing injuries to the bones. It is also especially useful in 



3° 



Physiology. 



locating a bullet or other solid body in the flesh, which 
probing often fails to discover. 

Levers. — The main facts to be learned about a lever are. 
that it is a rigid bar ; the point about which the lever turns 
is called the fulcrum ; the place where the power is ap- 
plied is called the power ; and the part to be moved is 
called the weight. In the body, the fulcrum is some joint, 
the power is the place where the muscle is attached, and 
the weight is the part to be moved. 

Kinds of Levers. — There are three kinds of levers. In 
the first class the fulcrum is between the power and the 
weight, as in prying over a block with a crowbar. In 
the second class the weight is between the power and 
the fulcrum, as in a wheelbarrow. In the third class the 




(!) Tapping on Floor. (2) Rising on Toe. (3) Lifting Weight 

Fig. 19. Three Kinds of Levers as shown by the Foot. 
P — Power. W — Weight. F — Fulcru m . 

power is between the fulcrum and the weight, as in rais- 
ing the forearm (see upper part of Fig. 19). We may 
find many examples of levers in the body if we look for 
them. 

Kinds of Levers shown by the Foot. — The different 



The Muscles and the Bones. 



3 1 



; Ball 



Articular Extremity 



classes of levers may be illustrated by different motions 

of the foot. In tapping the toes on the floor while 

the heel is lifted, or in pressing down the ball of the 

foot while running the treadle of 

a sewing machine, we have an 

example of a first-class lever. In 

raising the weight of the body on 

tiptoes, or as the foot is used in 

taking each step, the foot is used 

as a lever of the second class. 

When one lifts a weight with the 

toes, the foot is used as a lever 

of the third class. (See Fig. 19.) 



Medullary Cavity 



Hard Bone 



Advantages of Levers in the Body. — 

If the arm consisted merely of the biceps 
muscle, suspended from the shoulder, it 
is evident that its only action would be 
a straight pull. Suppose the biceps, 
thus hanging alone from the shoulder, 
had a hook at its lower end, it could, 
when it shortened, lift a weight just as 
far as it shortened, and no farther. It 
could not swing the weight outward, or 
push it upward. But from the way in 
which the biceps is attached to the fore- 
arm (see Fig. 10), when the muscle 
shortens an inch it may move the hand Fig. 20. 
a foot. Of course the hand moves much 
faster, and we have a great gain in speed by reason of this lever arrange- 
ment. But we cannot lift so heavy a weight at this faster rate, as we 
could at the elbow. 



— : Spongy Bone 

- Articular Extremity 

Longitudinal Section of 
Femur. 



Study of One of the Long Bones. — For this, take, preferably, a femur 
or a humerus. Let us suppose we have a femur. 

1. Observe its shape, — cylindrical, somewhat curved, enlarged at 
the ends. 



32 



Physiology. 



2. The ends have smooth places, where they fitted other bones. 

3. Along the sides, especially near the ends, are ridges and projec- 
tions, where the muscles were attached. 

4. There are small holes in the bone, where blood tubes passed in 
and out. 

5 . Saw a femur in two, lengthwise, and make 
a drawing showing : — 

(#) The central marrow cavity. 
(d) The spongy extremities, noting especially 
the directions of the bony plates and fibers. 

6. Observe the width of the lower end of 
the femur, where it rests on the tibia. Sup- 
pose these two bones were as narrow at their 
ends, where they meet to form the knee joint, 
as they are at their centers, what kind of a joint 
would they make ? Illustrate by piling up a 
number of spools on end ; the column is more 
lightened than it is weakened by the hollow- 
ing out of the sides of each spool. And the 
central hollow of the spool does not greatly 
weaken it. 

Joints. — The ends of the bones, where they 
fit together in the joints, are covered with a 
layer of smooth, elastic, whitish or transparent 
cartilage. The motion in the joints is made 
still more easy by the synovia, resembling white 
of egg. The ends of the bones are held to- 
gether by tough bands and cords of liga?nent^ 
a form of connective tissue very much like ten- 
don. Bones are closely covered by a tough 
coat of connective tissue called the periosteum. 

All these structures can easily be found by 
dissecting a sheep shank gotten from the 
butcher, or in the hind leg of a rabbit. 




Fig. 2 1 . Action of the Mus- 
cles in Standing. 



Standing. — Although we are not ordinarily conscious 
of the fact, when we are standing still we are using many 
muscles. The accompanying figure illustrates how some 
of the muscles act in keeping the body upright. Our 



The Muscles and the Bones. 33 

■weight, or, we would better say, the force of gravity, is 
continually trying to pull us down to the ground. The 
joints are all freely movable, and hence as soon as the 
muscles cease to act properly, in balancing against each 
other, we lose our balance, and fall if we do not quickly 
regain it. 

Walking. — In walking, we lean forward, and if we take 
no further action we fall. But we keep one foot on the 
ground, pushing the body forward, while the other leg is 
bent and carried forward to save us from the fall. We 
catch the body on this foot, and repeat the action. To 
show how we are really repeatedly falling and catching 
ourselves, recall how likely one is to fall if some obstacle 
is placed in the way of the foot as it moves forward to 
catch the weight of the body. 

Running. — In running, the action is more vigorous. 
The force exerted by the rear leg is now greater. It gives 
such a push as to make the body clear the ground, whereas 
in walking, the rear foot is not lifted till the front foot 
touches the ground. But in running there is a time when 
both feet are off the ground. 

Locomotion by Reaction. — Take two broomsticks and place them 
crosswise under the ends of a board. Run along the board. This 
shows that the direct effort in running is to push one's support from 
under him. Our effort in moving forward is to push the earth out from 
under us, and it is by reaction that we go forward. It is the same 
problem with the fish swimming forward by striking backward and 
sideways against the water, and with the bird beating downward and 
backward upon the air. 

Bones combine Lightness and Strength. — The muscles, 
then, make use of the bones as levers. We carry these 
levers with us all the time. Hence the desirability of hav- 
ing them light as well as strong. A hollow pillar or hoi- 



34 



Physiology. 



low tube has greater strength than the same amount of 
material in the form of a solid cylinder. The long bones 
of the limbs are hollow, and near their ends, where we 
have found that they need to be enlarged, we find a 
spongy structure, where lightness and strength are secured 
by the interlacing fibers and plates of bony material. 

Muscles always Stretched. — The muscles are always 
slightly stretched, as shown by the fact that when a cut 

is made into a muscle the 
wound gapes open ; the ten- 
sion of the muscle is further 
shown by the fact that when 
a bone is broken, as in the 
upper arm or thigh, the ends 
of the bones may slip by each 
other, and the limb has to be 
strongly stretched to bring the 
ends back together. Muscles 
act better when slightly 
stretched, and probably need a 
slight resistant action of the 
opposing muscle. 




Fig. 22. Fracture of the Humerus. 



What makes the Muscles act 
in Harmony ? — Have you ever 
seen two persons, one using the right hand and the other 
the left, try to sew, one holding the cloth, the other using 
the needle ? Would they get along well ? Suppose one 
were to hold the needle, and the other were to try to thread 
it, each using one hand. Why is it that the right and left 
hands of two persons cannot work so well together as the 
right and left hands of one person ? What connection is 
there between the two, that one knows just what the other 



The Muscles and the Bones. 35 

is doing and when it does it ? Why can two individuals 
never, with any amount of practice, work so in unity as the 
parts of the individual ? 

Let us seek the answer to these questions in the follow- 
ing lessons. 

Reading. — " How to Get Strong and How to Stay So," Blaikie, 
" Sound Bodies for Our Boys and Girls, 11 Blaikie. 

Summary. — i . In the limbs the muscles are spindle-shaped and have 
their greatest diameter opposite the central, or narrower, portions of the 
bones, concealing the fact that the bones are largest at the ends, as is 
so evident in the skeleton. 

2. The bones serve as levers by which the muscles exert their force. 

3. The bones of the limbs are hollow cylinders combining lightness 
and strength. 

4. The joints have a smooth motion due to the cartilage and synovia. 

5. Locomotion is brought about by reaction. 

Questions. — i. Find other examples of levers in the body. 

2. Find examples of the three kinds of levers, not in the body, which 
we use often. 

3. Why is it easier to sit with one leg crossed over the other ? 

4. How may the arms be used to illustrate the three kinds of levers ? 

5. Analyze and explain jumping, hopping, etc. 



CHAPTER V. 

THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM. 
— SENSATION AND MOTION. 

What makes Muscles Shorten? — We have seen that the 
muscles have the power of shortening ; that in shortening 
they act on the bones as levers to produce our varied mo- 
tions. What makes the muscles shorten? 

Voluntary and Involuntary Motions. — Some motions we 
will to make. We will to sit, to stand, to walk, to run, or 
to stretch out the hand. Such motions, originating in a 
brain activity, are called voluntary. Other motions are 
involuntary. The will does not control the heart-beat. 
Most persons cannot keep from winking when a quick 
motion is made toward the face, even if they know they 
will not be hit. But all of these motions, both voluntary 
and involuntary, depend upon the nervous system. 

The Cerebro-spinal Nervous System. — This consists of 
the brain, the spinal cord, and the spinal nerves. 

The Brain. — There are two main parts of the brain, the 
cerebrum, which fills all the upper part of the cranium, 
and the cerebellum, very much smaller, in the lower back 
part of the cranium. The cerebrum is divided into right 
and left hemispheres by a lengthwise groove. The sur- 
face of the cerebrum is covered with ridges called convo- 
lutions. The outside of the brain is of gray matter, 
consisting of cells, while the inside is white, consisting of 
nerve fibers, 

36 



Nervous System. 



V 




Fig. 23. The Cerebro-spinal Nervous System. 



Two Functions of the Brain. — Only two functions of the 
brain are to be noticed now. One is se?isatio7i y the other 
motion, or rather the control of motion. Nerve currents 
that come to the brain, produce all our sensations. Sen- 



38 Physiology. 

sation is in the gray matter on the outside of the brain. 
When we wish to move any part of the body, the first 
thing is to will to do it. This action is also in the gray 
matter on the outside of the brain, but in different parts 
from those which have sensation. The act of willing to do 
anything sends nerve currents, or impulses, along nerve 
fibers to the part that is to be set to work. The white 
fibers of the inside of the brain connect the cells of the 
gray matter with the various parts of the body through the 
base of the brain, the spinal cord, and the spinal nerves. 

The Spinal Cord. — The spinal cord is a cylindrical body 
extending from the brain along the cavity of the spinal 
column. Its diameter is not uniform throughout. Between 
the shoulders is an enlargement called the cervical enlarge- 
ment, where the large nerves are given off to the arms. 
In the region of the loins is the lumbar enlargement, where 
the nerves are given off to supply the legs. The outside 
of the cord is white, but the central portion consists of 
gray matter. The white portion is made up of fibers, but 
the gray matter consists of nerve cells as well. 

The Spinal Nerves. — These are given off in pairs from 
the sides of the spinal cord. They pass out through notches 
between the successive vertebras, so there is no danger of 
their being crushed, or even pinched, when the backbone 
bends. In the regions of the shoulders and loins the 
spinal nerves are large, as they supply the large muscles 
of the limbs ; but in the middle of the back, where only 
the muscles of the body wall are supplied, the nerves are 
small. We have thirty-one pairs of spinal nerves. 

The Roots of the Spinal Nerves. — Each spinal nerve 
arises by two roots, one nearer the back, called the dorsal 



Nervous System. 39 

root, the other nearer the ventral surface, the ventral root. 
These two roots soon unite to form one spinal nerve. 

Structure of Nerves. — If we trace a nerve outward, we 
find that it is continually subdividing. This division con- 
tinues until the branches are too small to be seen by the 
naked eye. Microscopic examination shows that a nerve 
is made up of a great number of fibers bound together in 
a common sheath of connective tissue, as is the case with 
muscle. When the nerve divides, there is ordinarily no 
true branching or forking, but certain of the fibers simply 
separate from the rest, as in the separation of the fibers in 
floss silk. 

Nerve Fiber Sheath 
/ 



Axis Cylinder 



Medullary Sheath 
Fig. 24. Structure of a Nerve Fiber. 

Structure of a Nerve Fiber. — A single nerve fiber is too 
small to be seen by the naked eye, being only about one 
two-thousandth of an inch in diameter. It consists of the 
following parts : — 

1. The axis cylinder, a central strand, or core, of semi- 
transparent, gray material. 

2. The medullary sheath is a layer of white, oily ma- 
terial around the axis cylinder. 

3. The nerve fiber sheath is a thin, transparent outer 
sheath of connective tissue. 

Function of Nerve Fibers. — The only function of the 
nerve fiber is to convey nerve impulses. The nerve im- 
pulse passes along the axis cylinder as an electric current 
passes along an insulated wire. 




4 o 



Physiology. 



Afferent and Efferent Nerve Fibers. — Nerve fibers that 
carry impulses toward the spinal cord or brain are called 
afferent nerve fibers. Fibers that convey impulses from 
the brain or spinal cord are efferent nerve -fibers. 

Cross-section of the Spinal Cord. — If a thin slice of 
the spinal cord be made as shown in Fig. 25, it will be 
seen that the central part is darker in color than the outer 
part. The central part is known as the gray matter, in 
distinction from the rest, which is called the white matter. 

Dorsal Septum 



Dorsal or Senso 
Root 




Ventral Fissure 
Ventral or Motor Root 

Fig. 25. Cross-section of Spinal Cord. 

The white matter of the nervous system is made up of 
nerve fibers, whose structure and use we have just con- 
sidered. But the gray matter has a different structure and 
a different function. Instead of being made up mainly of 
fibers, it is composed of cells, one of the forms of which is 
represented in Fig. 26. Some of the branches of these 
cells are continued, and become the axis cylinders of 
nerves, and it is believed that every nerve fiber begins as 
a branch of some nerve cell. 



Nervous System. 



4i 




Fig. 26. A Large Nerve Cell from the 
Gray Matter of the Spinal Cord. 



Functions of the Spinal Cord. — The spinal cord has two 
main functions : — 

1. Its conducting power, by means of the white fibers 
which make up the outer part of the cord. These fibers 

connect the gray matter of 
Pr>nc the brain with all parts of the 

body, and carry messages to 
and from the brain. 

2. The gray matter is the 
center of the reflex actions of 
the cord. 

Ganglions. — Masses of 
nerve cells make up nerve 
centers, or ganglions, such 
as are on the dorsal roots of 
the spinal nerves. These 
also would show under the 
microscope that their chief constituent is a collection of nerve 
cells which give off one or more branches. The gray matter 
of the spinal cord is a collection of ganglions. 

Reflex Action in a Sleeping Child. — If the sole of the foot of a sleep- 
ing child is gently tickled, the foot will be drawn up. The child has no 
sensation. The brain has nothing to do with it. It is purely reflex 
action. A nerve impulse has gone to the spinal cord, and another 
impulse has been sent out to make the needed movement. But some- 
times the child may be half awake and the foot might be drawn up by 
voluntary action. Let us take another case, with which nearly every 
one is familiar, to show that the brain has nothing to do with reflex 
action. 

A Hen with its Head cut off. — Nearly everybody knows that after a 
hen's head is cut off, it " flops " around for some time, and that fre- 
quently when one takes hold of its feet to pick it up, it begins to struggle. 
Now this also is reflex action of the spinal cord. And there can be no 
doubt that the brain has nothing whatever to do with it. 
4 — phy 



42 



Physiology. 



The Gray Matter of the Cord the Center of Reflex 
Action. — In reflex action the current runs up the nerve 
to the spinal cord. The gray matter of the central part of 



Afferent Dorsal Root 

Sensor Fiber / 




Muscle 



Motor Fiber - 
Efferent 



Fig. 27. 



Ventral Root 

Diagram of Reflex Action of the Spinal Cord. 
(After Landois and Stirling. ) 



the cord receives the message, and sends back a nerve 
impulse to the muscles, to make them shorten and pull the 
foot away from the source of irritation. 

The Parts Essential to Reflex Action of the Spinal 
Cord: — i. A sensitive surface (the skin, for instance). 
2. Afferent nerve fibers. 3. A nerve cell, or cells, in 
the center of the spinal cord. 4. Efferent nerve fibers. 
5. Working organ, as muscle or gland. 

Steps in Reflex Action. — In the above examples the 
steps in order are : — 

1. Stimulation of the nerve endings in the skin of the 
foot. 2. Passage of nerve impulses up the afferent fibers 
to the spinal cord. 3. Reception of the impulse by cells 
of the gray matter in the cord. 4. Sending back nerve 
impulses. 5. Along efferent fibers to 6. Muscles which 
shorten so as to move the foot. 



Nervous System. 43 

Importance of Reflex Action. — It is important that we 
understand the nature of reflex action, for very many of 

the processes of the body are regulated by it. Not only 
such motions as winking when anything comes quickly 

Nerve Cells Connected by Interlacing Nerve Network. 



Afferent Nerve Fiber 



Sensory 

Epithelium 

<Sk,n> 




Efferent Nerve Fiber 



Fig. 28. Parts used in Reflex Action. 



toward the eye, dodging, jumping when suddenly touched 
by anything hot or when pricked by a pin, but also the 
regulation of circulation, respiration, and digestion, are 
brought about through reflex action. 

Destination of Nerve Fibers. — The sciatic nerve (the 
large nerve of the thigh, see Fig. 23) is composed of many 
fibers. If this nerve is traced outward, it is found to be 
continually subdividing and sending smaller branches to 
the muscles, and finally in the muscles one fine nerve fiber 
goes to each muscle fiber. (See Fig. 13.) Many fibers go 
on past the muscles to the skin. We can feel in any part 
of the skin, and we can tell just where we are touched. 



44 Physiology. 

These fibers from the skin carry nerve impulses inward, 
as those going to the muscles carry impulses outward. 

Nerve Roots and their Functions. — Observations made 
on animals, and accidents in the case of man, show that 
all the fibers of the nerves that carry currents to the mus- 
cles pass out from the spinal cord into the ventral root, 
and that all the fibers that carry currents inward enter the 
spinal cord through the dorsal root. Hence, the dorsal 
root is often called the afferent root, and the ventral the 
efferent root. Since ingoing impulses produce sensation, 
the dorsal root is called the sensory root, while the ventral 
root, carrying currents outward to produce motion, is called 
the motor root. 

Effect of Stimulating a Spinal Nerve. — Experiments 
have shown that if, in an uninjured animal, a nerve, or 
more properly a nerve trunk — as the sciatic nerve — be 
stimulated, for instance, by an electric shock, two effects 
are produced : first, motion in the parts whose muscles are 
supplied by the nerve ; second, sensation, which is referred 
to the parts of the skin supplied by the branches of the 
nerve. This double effect is because both sets of fibers in 
the nerve have been stimulated, one set carrying currents 
inward, the other outward. 

Cramp. — Cramp is a spasmodic shortening of the mus- 
cles, attended with pain. 

Tetanus. — Tetanus (or locked jaw) is a spasmodic and 
continuous shortening of the muscles, causing rigidity of 
the parts they supply. It is due to the disordered and 
excessive stimulation of the muscles through the nerves. 

Crossing of the Fibers from the Brain to # the Spinal 
Cord. — ■ Both the brain and the spinal cord consist of two 
lateral halves connected by cross fibers. Each half of the 



Nervous System. 45 

brain is connected with the opposite half of the body. 
This is accomplished by the crossing of the fibers. The 
fibers that carry nerve impulses outward cross as they 
leave the brain, at the very beginning of the spinal cord, 
in the part known as the spinal bulb. The sensations 
arising from touching anything with the right hand, there- 
fore, are in the left half of the brain, and the right half of 
the brain controls the left hand. 

Nervous System compared to a Telegraph System. — 
It is convenient to compare the nervous system to a tele- 
graph system. Nerve impulses pass along the nerve fibers 
as electric currents travel along the wires. The ganglions, 
which receive and send impulses, are similar to the offices 
which receive and send out electric currents. But there is 
one important difference : in telegraphing, the same wire 
is used, both for sending and receiving messages-; while 
in the nervous system there are two sets of fibers, one for 
incoming impulses and another for outgoing impulses. 

Harmony in Muscle Action. — In throwing a stone a 
number of muscles are used. Each muscle shortens under 
the influence of a nerve impulse started by the brain and 
brought by a motor nerve. If any muscle shortens too 
soon, or a little too strongly, the stone goes to one side. 
In a tune on a piano we know that the right keys must be 
struck at the right time, and with the proper force. What 
the player is to the instrument, the brain is to the body. 

Temporary Loss of Muscular Power. — It may have hap- 
pened that after sitting long in one position you attempted to 
stand, but could not. One leg failed to act at the bidding 
of your will. When the foot is " asleep " we get little sen- 
sation from it; we hardly know whether it is touching the 
floor. Pressing on it with the other foot causes no pain. 



46 Physiology. 

The brain starts the nerve currents, and they run along 
the nerve as far as the compressed part; here they stop. 
On account of external pressure the nerve has temporarily 
lost its power of conducting nerve currents. They cannot 
reach the muscles of the leg below. Hence the muscles 
do not shorten, and we do not rise, no matter how strongly 
we will to do so. 

Dependence of Nerves and Muscles. — But what beside 
the nerve has been compressed ? What process in the 
limb has been interfered with by the pressure due to the 
position in which one has been sitting or lying ? What is 
the temperature of the benumbed limb ? 

On what are the nerves and muscles so dependent for 
keeping up their activity ? 

Summary. — 1 . Motions are voluntary or involuntary, but all are 
under control of the nervous system. 

2. The cerebro-spinal nervous system consists of the brain, the 
spinal cord, and the spinal nerves. 

3. Each spinal nerve has two roots: the dorsal, which is afferent 
and sensory ; the ventral, which is efferent and motor. 

4. A ganglion is a nerve center largely composed of nerve cells. 

5. Nerves are made up of nerve fibers. 

6. A nerve fiber consists of the central core (or axis cylinder), 
which conducts the nerve impulse, the medullary sheath, and, outside, 
the nerve-fiber sheath. 

7. The spinal cord has in its outer part white nerve fibers ; in its 
center, gray nerve cells. 

8. These cells are branched, and at least one branch becomes the 
axis cylinder of a nerve fiber. 

9. The gray matter of the cord is the center of the reflex action, 
to. The nerve fibers from each half of the brain connect with the 

opposite half of the body. 

11. The nervous system is comparable to a telegraph system. 
Questions. — 1. Name as many involuntary motions as you know. 

2. What other cases of reflex action do you know ? 

3. Why is a man partially paralyzed when he has broken his back ? 



CHAPTER VI. 
CIRCULATION OF THE BLOOD. 

The Blood and its Work. — There is no bleeding when 
we trim the nails or cut the hair, and the outer skin has 
no blood in it. But the inner skin, and almost every tissue 
within it, if pierced even by the finest needle, yields blood. 
We know that loss of blood causes weakness, and may 
soon cause death. 

What kind of a substance is blood ? Why is it so 
essential to life? How does it do its work? 

The Rate of the Heart Beat. — The heart beats about 
seventy-two times a minute. In children it beats faster. 
The rate is increased by exercise, by heat, by food, and by 
mental excitement. 

The Heart Beat and the Pulse. — i. The heart beat may be felt at the 
left of the breastbone. 

2. The pulse may be felt at the wrist, in the neck beside the wind- 
pipe, and in various parts of the body. Perhaps the most convenient 
place to study it is at the temple. Lay the forefinger lightly along the 
cheek just in front of the ear. Count the pulsations for a minute. 

3. Let one or two pupils step to the blackboard and put down the 
number of pulsations of each pupil, and divide by the number thus 
reporting, to get the average. 

4. Let all count the pulse while sitting. Get the average of the 
class. 

5. Find the pulse while sitting ; rise quickly, and immediately begin 
to count the pulse. Compare with the pulse as taken while sitting. 

6. Compare the pulse before and after meals. 

47 



48 Physiology^ 

The Shape of the Heart. — The heart is cone-shaped. 
But the point or apex is down, and the big end, or base, 
is up, so when we speak of the base of the heart we mean 
the upper part, not the lower. 

The Position of the Heart. — The base of the heart is 
in the center of the chest, just back of the breastbone, 
but the apex points downward and to the left (see Figs. 
32 and 53). 

To Head and Arms 
Pre-caval Vein* 



Right AuncleJF ~^g^^ m^ST Pulmonar y Artery 

■ Left Auricle 



Left Ventricle 




Apex 



Fig. 29. The Heart, from the front. 



The Size of the Heart. — A person's heart is about the 
size of his clenched hand. 

The Covering of the Heart. — The heart is inclosed in a 
loose-fitting bag, the pericardium. Within the pericardium 
and around the heart is a small quantity of liquid, called 
the pericardial fluid. 

The External Features of the Heart. — The larger part 
of the heart is made up of ventricles, the auricles being 
two ear-like flaps at the base, one on each side. There 
is a deep notch between the auricles and the ventricles. 



Circulation of the Blood. 49 

The line of division between the two ventricles is marked 
bv a groove, which runs obliquely along the front surface. 
In this groove are blood tubes and usually some fat. (See 
Figs. 29 and 30.) 

The Internal Structure of the Heart. — The two halves 
of the heart are completely separated from one another by 
a partition. Each half has valves which, part of the time, 
separate the cavity of each auricle (at the base) from the 
cavity of the ventricle (at the apex). 



Aorta (j^ ^fyf g^^^ Pre caval Vein 

Left Pulmonary Artery _ 



Left Pulmonary Veins 
Left Auricle 




Right Pulmonary Artery 
Right Pulmonary Veins 



Post-caval Vein 



ght Auricle 



Fig. 30. The Heart, from behind. 

The Valves of the Heart. — Between the auricles and the 
ventricles are curtain-like valves (see Fig. 33), whose 
upper edges are attached to the inner surface of the walls 
at the upper margin of the ventricle. These flaps are 
somewhat triangular, and have strong, white, tendinous 
cords extending from their edges and under surfaces to 
the walls of the ventricle below. In the right half of the 
heart there are three flaps, and this valve is called the 
tricuspid valve. In the left side there are two flaps, which, 
together, make up the mitral valve. In the resting heart 



50 Physiology. 

these flaps hang down along the walls of the ventricles so 
that on opening the heart one would see only a single 
cavity in each half of the heart. 

The Aur-vent Valves. — Since these valves are between 
the auricles and the ventricles they are often called the 
auriculo-ventricular valves. Nearly every one knows of the 
town named Pen Mar on the line dividing Pennsylvania 
from Maryland. The meaning of the name is clear. And 
any one can tell where Texarkana must be. So for con- 
venience we shorten auriculo-ventricular to aur-vent, and 
when speaking of the aur-vent valves we. know, without 
having to stop and think, that they are between the auricles 
and ventricles. 

The Semilunar Valves. — From the base of the right 
ventricle arises the pulmonary artery. Within its base, 
just as it leaves the ventricle, are three pocket-like valves, 
like " patch-pockets." They are in a circle, with their 
edges touching, and thus surround the opening, with their 
mouths opening away from the heart. A similar set of 
valves are within the base of the aorta, which arises from 
the left ventricle. Both these sets of valves are called 
semilunar valves. As they are between the ventricles and 
the arteries they are sometimes called the ventriculo-arterial 
valves. And this may be shortened to vent-art valves. 
(See Fig. 33.) 

Dissection of the Heart. — No description (or even pictures) can 
give a clear idea of the heart. A good model will be of some assist- 
ance. But the heart itself should be examined carefully and then dis- 
sected. The heart and lungs of a sheep should be obtained (ask the 
butcher to save the "pluck," i.e. the heart and lungs taken out together). 
The relations of the heart to the lungs and other organs should first 
be studied, and then the pericardium opened. Observe the outside of 
the heart, and then cut the heart open to see the points given in the 



Circulation of the Blood. 



5 1 




E 



52 Physiology. 

above description. After the heart is severed from the lungs the auri- 
cles may be cut off; then, by pouring water into the ventricle, the 
action of the valves between the auricles and the ventricles will be 
seen. Pressing on the outer surface of the right ventricle will make 
the water escape through the pulmonary artery. If this be split open, 
the semilunar valves at its base may be found. 

The Blood Tubes connecting the Heart with Other 
Organs. — The aorta arises from the left ventricle. The 
pulmonary artery springs from the right ventricle and 
sends blood to the lungs. The pre-caval and the post-caval 
veins enter the right auricle. The pulmonary veins, two 
from each lung, enter the left auricle. (See Figs. 31 and 32.) 

The Aorta. — The aorta is the largest artery in the body. 
It arises from the base of the left ventricle and runs a 
short distance toward the head, then it arches over and 
runs toward the lower part of the body. The bend, above 
the heart, is called the arch of the aorta. At the arch 
branches are given off which supply the right and left 
arms, and the right and left sides of the head. Beyond 
the arch the aorta passes behind the heart and runs along 
the backbone and passes through the diaphragm. Just 
beyond the diaphragm it gives off branches to the liver, 
stomach, intestine, pancreas, and spleen. It gives a 
branch to each kidney, and finally divides into two large 
branches to the lower limbs. Numerous small branches 
are sent to other organs; in short, the aorta supplies 
blood to every organ of the body except the lungs. (See 
Figs. 29, 30, and 32.) 

The Caval Veins. — There are two caval veins, the pre- 
caval and the post-caval. The pre-caval brings the dark 
blood from the head and arms. It has four main branches, 
one from each side of the neck, the jugular veins ; and 
one from each arm, the subclavian veins. These four 



Circulation of the Blood. 



53 



d External Jugular Vein 

nternal Jugular Vein 



2 Subclavian Artery 

ubclavian Vein 
1 Carotid Artery 



i Aorta 
trr Precaval Vein 




iv Postcaval Vein 



Gastric Artery 
Splenic Artery 
Hepatic Artery 
Pancreatic Artery 



Fig. 32. Distribution of Arteries and Veins. 



54 Physiology. 

unite to form the pre-caval vein, which runs downward and 
enters the right auricle. The post-caval vein begins in the 
lower part of the abdomen, by the union of the two large 
veins from the lower limbs. As it funs upward, it receives 
branches from the kidneys and from the liver; it passes 
through the diaphragm and enters the right auricle. (See 
Figs. 29, 30, and 32.) 

The Distribution of the Arteries and Veins. —- The organs 
of the body receive a supply of blood in proportion to 
their size and activity.. The artery supplying the blood to 
any organ and the vein which returns it usually lie side 
by side (see Fig. 32). The larger arteries are usually 
deep-seated and in protected places. 

The Action of the Heart. — The heart consists of muscle 
fibers so arranged that they form a thick-walled bag, which 
stands expanded when the muscles relax. But when the 
fibers shorten, the heart contracts and the blood is forced 
out. 

The complete action of the heart consists of three parts, 
— the contraction of the auricles, the contraction of the 
ventricles, and the pause. 

The Pause. — During the pause the blood is steadily 
pouring into the auricles ; into the right auricle from the 
caval veins, into the left auricle from the pulmonary veins. 
The aur-vent valves are now open, and their flaps hang loosely 
beside the walls of the ventricles. The blood, therefore, 
instead of stopping in the auricles, passes on into the ven- 
tricles. As the ventricle fills, the aur-vent valves float up, 
as seen in the experiment of pouring water into the ven- 
tricle. (See right-hand part of Fig. 33.) 

The Contraction of the Auricle. — When the ventricle is 
full, but not stretched, and the auricle partly full, the auricle 



Circulation of the Blood. 



SS 



suddenly contracts, thus forcing more blood into the ven- 
tricle, and distending it. At the same time the aur-vent 
valves, which were already nearly closed, are tightly closed 
by the pressure of the blood which is forced up behind 
them. The flaps of the valves are kept from going up too 
far by the tendinous cords and by the muscles to which 
the cords are attached. 




Fig- 33. Diagram of the Heart, showing the Action of the Valves. 



The Contraction of the Ventricle. — Next comes the con- 
traction of the ventricle, slower, but more powerful than 
that of the auricle. As the walls of the ventricle are 
drawn together, they press upon the blood. It cannot go 
back into the auricles, for the more it presses against the 
aur-vent valves, the more tightly they are closed. The 
vent-art (semilunar) valves are closed by back pressure in 
the aorta and pulmonary artery. But the pressure of the 
blood in the ventricles is so much greater that the vent-art 
valves are forced open, and the blood is driven out of the 
ventricles; from the right ventricle into the pulmonary 
artery, and from the left ventricle into the aorta. 

While the ventricles are contracting and forcing their 



56 Physiology. 

blood out, the auricles are slowly filling by the steady 
inflow through the veins. 

Systole and Diastole. — The contraction of the heart is 
called the systole, and its dilation is the diastole. 

Dilation of the Ventricle. — As soon as the ventricle has 
completed its contraction it dilates, and most of the blood 
that has accumulated in the auricle simply falls into the 
ventricle. The dilating ventricle makes a slight suction, 
so the blood is in part drawn into the ventricle. During 
the remainder of the pause the blood accumulates in the 
ventricle and auricle till the auricle again contracts and 
the action is repeated. This is true of both halves of the 
heart, which work at the same time, the two auricles con- 
tracting together, and then the two ventricles. The right 
heart pumps dark blood while the left heart pumps bright 
blood. The left ventricle is thicker walled and stronger 
than the right. 

Work and Rest of the Heart. — Immediately after the 
contraction of the auricle comes the contraction of the 
ventricle. The pause is as long as the contractions of 
the auricle and ventricle put together. In other words, 
the heart is resting half the time. It is often said that the 
heart never rests. Its periods of work and rest are so short 
and follow each other in such rapid succession that it is 
hard for us to realize that there is a resting time between 
each two beats, and that this resting time is as long as the 
working time. 

Overworking the Heart. — During violent exercise the 
heart is likely to be overworked trying to pump blood 
enough to supply the overworked muscles. One very 
important part of training an athlete is to strengthen the 



Circulation of the Blood. $'J 

heart by regular exercise so it will not tire out in pumping 
the blood to the muscles during an athletic contest, such as 
a foot race or boat race. 

The Work of the Auricle. — The auricle has three func- 
tions: (i) to complete the filling of the ventricle; (2) to 
complete the closing of the aur-vent valves ; (3) to act as a 
reservoir for the blood entering the auricle while the ven- 
tricle is contracting, that is, while the aur-vent valves are 
closed. 

The Work of the Ventricle. — The contraction of each 
ventricle forces the blood around to the ventricle of the 
other side of the heart. 

The Sounds of the Heart. — There are two sounds of the 
heart : — 

1. A short, sharp sound made by the closing of the 
semilunar valves. 

2. Just preceding this sound a longer, duller sound may 
be heard during the contraction of the ventricles. This is 
supposed to be due to the vibrations of the walls of the 
ventricles and of the aur-vent valves. 

Action of the Large Arteries. — The arteries have elastic 
tissue in their walls. When the blood is forced into them, 
they are stretched. As soon as the ventricle ceases to con- 
tract, and sends no more blood into the arteries, they 
" stretch back," We should not say contract, for it is 
simply an elastic reaction. As the artery reacts it presses 
on the blood, and hence the blood tries to escape in every 
possible way. It cannot go back into the ventricles, for it 
fills the pockets of the semilunar valves, and closes them 
with a click. The blood therefore flows along the arteries, 
through the pulmonary artery to the lungs, and through 

5— PHY 



5§ 



Physiology. 



the aorta and its branches to all the other parts of the 
body. 

The elastic reaction of the arteries thus helps to make 
steady the flow of blood, which is jerky as it leaves the 
heart. 

Variation of the Amount of Blood needed. — Each organ 
requires a supply of blood in proportion to its activity. 
An actively working organ, like the brain, demands much 
more blood than does such an inactive organ as a bone. 
Further, the working tissues, such as the brain and mus- 
cles, need a great deal more blood while they are at work 
than when they are resting. An organ needing a large 
supply of blood all the time might secure this by having a 
large artery. But how can the supply be regulated so that 
an organ may receive, now more, now less, according to its 
needs ? 

Plain Muscle Fibers in the Walls of the Arteries. — This 
is regulated by the medium-sized and small arteries leading 

to the parts. In the walls of these 

'fell! 1! 7" UC 6US arteries are plain muscle fibers. 

They are arranged circularly in the 
walls of the arteries (see Fig. 36). 
These fibers have, like all muscle 
fibers, the power of shortening. 
When they shorten they reduce 
the size of the artery, and, there- 
fore, for the time, less blood can 
flow through it. When the muscle 
fibers relax, the artery widens, and 
allows more blood to pass through it. 




Isolated Fiber' 



Fibers Joined 



fflVCT'll 
Fig. 34. Plain Muscle Fibers. 



Illustration of the Action of Muscles in Arterial Walls. — To illus- 
trate the action of the muscles in the walls of an artery, let the water 



Circulation of the Blood. 



59 



nm through a hose or large rubber tube. Now, if a row of persons take 
hold of this tube, the grip of their hands is like that of the muscles. 



Connective Tissue 



Endothelium 



Nucleuses 




Muscle Fiber 



Fig. 35. Plain Muscle Fiber. Separate and in Wall of Artery. 



Endothelium 



When the hands tighten their grip, the size of the hole in the tube is 
made smaller, and less water is allowed to flow through it. When the 
hands relax, the tube, being elastic, 
allows more liquid to flow through it. 

Illustration of a Small Artery. — 
To represent a small artery, take a 
small, thin-walled rubber tube and 
wind a red thread around it. Now 7 , if 
the thread could shorten, it would 
make the tube smaller. 

The Action of Plain and Striated 
Muscles Fibers compared. — These 
plain muscle fibers are further like 
those of the skeletal muscles in that 
they are under the control of the 
nerves, but they are involuntary in 
their action. We cannot interfere 
with the action of these muscles, no 
matter how strongly we may will to do so. 
it, more blood goes to the muscles of the legs when we walk, more to 




Fig. 36. Coats of a Smail Artery. 
Without our thinking about 



6o 



Physiology. 



the brain when we are studying, to the digestive organs after eating, etc. 
The plain muscle fibers shorten at a much slower rate than the striated 

fibers. They are also slower in relaxing. 

Circulation of Blood in the Web of a 
Frog's Foot. — This is a beautiful sight. 
Here you may see, under the microscope, 
the active streams of blood. Small ar- 
teries divide to form capillaries, and capil- 
laries unite again to form the small veins. 
In the narrow capillaries the corpuscles 
may be seen moving along in single file, 
with barely width enough to pass through 
the slender tube. If you see this in the 
frog's foot, you can understand how the 
blood flows through all the active tissues 
of your body. (See Figs. 37 and 39.) 

the Capillaries. — The arteries 




Fig. 37. " Capillary Blood Tubes in 
the Web of a Frog's Foot, under 
a Low Power of a Microscope." 
From Hall's " Physiology." 



The Blood Flow in 

divide and subdivide, and 
become capillaries, which 
have connecting branches, 
forming a close network 
of tiny thin-walled tubes. 
These penetrate nearly 
every tissue of the body. 
The blood cannot do its full 
work till it is in the tissues, 
and to reach the tissues it 
must soak through the walls 
of the capillaries. The 
work of the heart and ar- 



Surface View 




Longitudinal Section 

Fig. 38. Capillaries, composed of a Single 
Layer of Cells. 



teries is to keep a slow and steady flow of blood through 
the capillaries, that the tissues may be constantly supplied. 

The Veins. — The capillaries, after penetrating the tis- 
sues, unite again to form small veins, which in turn unite 
to form larger ones, till finally two great veins, the pre- 



Circulation of the Blood. 



61 



cava! from the upper and post-caval from the lower part of 
the body, return the blood to the heart. The veins, like 



Walls of Capillaries 



Tissues of Web 



,*3UK* 




Fig. 39. Part of Frogs Web (highly magnified). 

the arteries, are smooth inside and elastic (though less 
elastic than the arteries). They are thinner-walled than 
the arteries (see Fig. 40) and collapse when empty, 



62 



Physiology. 




Muscular 
Coat 



Fig. 40- 



Cross-section of Small Artery 
and Vein. 



whereas the larger arteries stand open, after they are 
emptied of blood. There are many cross-branches unit- 
ing veins, so that if the flow 
is stopped in one vein, the 
blood can take a "" cross- 
road" into another large 
vein. This cross-branching 
may usually be seen on the 
back of the hand. 

The Valves in the Veins. 
— The only valves in the 
arteries are those at the be- 
ginning of the aorta and pul- 
monary artery. Many of the 
veins have similar pocket-like valves though less strong 
than those of the arteries. They are usually in pairs, but 
sometimes single or in threes. They all have the mouths 
of the pockets toward the heart, so that the blood flows 
freely toward the heart, but is kept from flowing the other 
way on account of the filling 
of the valves by the back 
pressure of the blood. When 
the blood is flowing through 
the veins toward the heart, 
the valves lie against the walls 
of the veins (see Fig. 41). 

Illustration of Valves in the Veins. 

• — Make a cloth tube (or take the open 
lining of a boy's coat sleeve) and F \g. 41. 

sew three patch-pockets on the in- 
side, in a circle, i.e. with edges touching each other. Make the pockets 
a little "full." Pour sand, shot, or grain through the sleeve first in 
one direction and then in the other. This shows how the valves fill 
and block the passage when there is back pressure of the blood. 




Vein laid 
open 



Valves of the Veins. 



Circulation of the Blood. 63 

Evidences of Valves in Our Veins. — i. With the forefinger stroke 
one of the veins on the hand or wrist toward the tips of the fingers. 

The veins swell out. The blood meets resistance in the valves of the 
vein. Their location may be determined by their bulging out during 
the experiment. 

2. Stroke a vein toward the body, and the blood is pushed along 
without resistance. 

3. Let the left hand hang by the side. Note the large vein along 
the thumb side of the wrist. Place the tip of the second finger on this 
vein just above the base of the thumb. Now, while pressing firmly 
with the tip of the second finger, let the forefinger, with moderate 
pressure, stroke the vein up the wrist. It may be seen that the blood 
is pushed on freely, but comes back only part way. It stops where it 
reaches the valves, filling the vein full to this point, but leaving it col- 
lapsed beyond, as shown by the groove. Remove the second finger, 
and the vein immediately fills from the side nearer the tip of the fingers. 

These experiments show that the blood in the veins moves freely 
toward the body, but cannot flow r outward to the extremities. 

Effect of Pressure on the Veins. — Since the valves in 
the veins open toward the heart, any alternating pressure 
on the veins helps to push the blood on toward the heart. 
The valves are most numerous in the veins near the sur- 
face and in the veins of the muscles. The pressure of the 
muscles during their action (thickening while shortening) 
produces pressure on the veins ; and as the muscles act 
for a short time only, and then relax, this alternate com- 
pression and release aids very much in moving the blood 
on toward the heart. 

How the Muscles help the Heart. — This effect is greater 
at the time the muscles need the most active circulation ; 
namely, when they are in action, and are using the most 
blood. The heart has power enough to pump the blood 
clear around from each ventricle to the auricle of the other 
side of the heart ; but this outside aid comes in good play 
to relieve the heart at a time when it has an unusual 



64 Physiology. 

amount of work to do, as when one is using a large num- 
ber of muscles vigorously. 

" Every active muscle is a throbbing heart, squeezing 
its blood tubes empty while in motion, and relaxing so 
as to allow them to fill up anew." 

Rate of Blood Flow in the Arteries and Capillaries. — The 

blood flows rapidly in the arteries, slowly in the capillaries. 
Why is this ? When an artery divides, the two branches 
taken together are larger than the one artery that divided 
to form them. Hence as the blood flows on it is continu- 
ally entering a wider and wider channel ; for if all the cap- 
illaries fed by the aorta were united they would make a 
tube several hundred times as large as the aorta. 

The Flow of the Blood compared with the Current of a 
Stream. — If we walk along a stream, we see that the 
channel keeps changing in width and depth. Where the 
channel is large, whether from increased width or depth, 
there the current is slower, but wherever the channel is 
reduced, the current is more rapid. So the stream in the 
comparatively narrow artery is swift. In the capillaries, 
although any single channel is small, these channels all 
together are wide ; the result is the same whether a river 
widens out into a single lake, or divides into a great num- 
ber of channels running past many islands. 

The Flow of Blood in the Veins. — When two veins unite, 
the one vein they form is not quite equal to the sum of the 
two ; so when the blood gathers in the veins it is really en- 
tering a narrower channel, and it flows faster. And it 
keeps gaining in speed till it reaches the heart. 

Flow in Arteries and Veins compared. — Although the 
blood keeps flowing fast as it gets nearer the heart in the 



Circulation of the Blood. 



65 



cava] veins, it does not go as fast as when it left the heart 
in the aorta, for there are two caval veins eaeh about as 
large as the aorta. 



Pulmonary Vein - 



Left Auricle 



Left Ventricle 



Aorta 



Digestive Tube 




Pulmonary Artery 
Lymph Vein 

Right Auricle 
Right Ventricle 
Caval Vein 

Liver 



Fig. 42. Plan of Circulation. (Back View.) 

Rate of Flow in Arteries, Capillaries, and Veins. — The 
blood flows rapidly in the arteries, slower in the veins, and 
slowest in the capillaries. 

Summary. — 1. The heart beats about seventy-two times a minute. 

2. The pulse is a wave running along an artery. 

3. The pulse varies with age, health, food, etc. 

4. The heart has two main cavities, one in each half of the heart, and 
two separate streams are flowing through it. 



66 Physiology. 

5. Valves allow the blood to flow through the heart in one direc- 
tion, but prevent its return. 

6. The heart is a hollow muscle, and by contraction forces the 
blood out into the arteries. 

7. The heart works about half the time. 

8. The large arteries, by elastic reaction, push the blood on while 
the heart is resting. 

9. Circular muscle fibers in the walls of the medium-sized arteries 
regulate the blood supply to the organs. 

10. In the arteries the blood flow is rapid and jerky, in the capillaries 
slow and steady. 

11. The thin walls of the capillaries allow the liquid part of the 
blood to soak out and nourish the tissues, and to soak back into the 
capillaries bearing waste matter. 

12. The veins are thin walled, and collapse when empty, while the 
arteries are thick walled, and stand open when empty of blood. 

13. Arteries carry blood from the heart, while veins carry it toward 
the heart. 

14. The veins have valves which allow the blood to pass toward 
the heart, but not away from it. 

15. Any alternating pressure on the veins aids the blood flow. 

16. The blood flow is most rapid in the arteries, slower in the veins, 
slowest in the capillaries. 

17. Gravity influences circulation. 

Questions. — 1 . Why do the large arteries lie deep ? 

2. In which direction should the limbs be stroked to aid circulation ? 

3. How does slapping the hands around the body warm the fingers ? 

4. How can a horse or a cow be comfortable with the head down ? 

5. Why are the walls of the left ventricle thicker than those of the 
right ? 

6. Trace a drop of blood from the tip of a finger around the circuit 
to the same point again. 

7. Does the pulse at the wrist occur at exactly the same time as at 
the temple ? Or at the same time as the heart-beat ? 



CHAPTER VII. 



CONTROL OF CIRCULATION. 



Circulation controlled by the Nervous System. — We 

know that fear often causes the face to turn pale and that 
shame makes it red. Certain emotions also 
quicken or retard the action of the heart. 
Great grief or joy has caused sudden death 
by stopping the action of the heart. 

Nervous Control Involuntary. 
— But this control is not volun- s ^ n ^ ^ c ^ 
tary. The will has nothing di- ^^^^^^ 

rectly to do with it. We often wish to keep 
from getting red in the face when embar- 
rassed, but cannot prevent it. Neither can 
we keep from turning pale through fright 
or pain. We cannot keep the heart from 
beating faster when we are excited. Instead 
of being controlled by the brain, circulation 
is chiefly under the control of a special part 
of the nervous system, known as the Sym- 
pathetic Nervous System. 

The Sympathetic Nervous System. — The 

sympathetic nervous system consists of two J[| 
rows of ganglions in the body cavity, one y j 

00 J J * Fig-. 43. F.-ont View 

along each side of the spinal column, re- of spinal cord with 

. . t , r . , Sympathetic Gan^- 

ceivmg branches from the spinal nerves, lions of One Side. 

67 



Carotid PI 



Superior Cervical Ganglion 



Middle Cervical Ganglion 




Fharyngeal Branches 
Cardiac Branches 

Deep Cardiac Plexus 

— - Superficial Caidiac Plexus 



Solar Plexus 



Aortic Plexus 



Lumbar Ganglions 



Fig. 44. Vertical Section of Body, showing Sympathetic Nerves and Ganglions of Right 
Side and their Connection with the Cerebro-spinal Nerves. 



Control of Circulation. 



6 9 



Sympathetic 
Ganglion 




and sending branches to the heart and lungs in the chest, 
and to the liver, stomach, and other organs in the abdomen. 

In many places these nerves form a thick network called 
a plexus. One very large plexus on the dorsal surface of 
the stomach is called the solar plexus. (See Fig. 44.) 

Regulation of the Size of the Arteries. — In the last chap- 
ter we learned that in the walls of the arteries are muscle 

fibers having a ring-like 

Spinal Cord ^ to 

arrangement. When these 
muscle fibers shorten they 
make the artery narrower, 
and less blood can flow 
through it. When the 
muscle fibers relax, they 

Fig. 45. Ideal Cross-section of the Nervous lengthen | the artery be- 

System. (After Landois and Stirling.) ° J 

comes wider, and more 
blood flows through it. Now these muscle fibers are under 
the control of the sympathetic nerves. The sympathetic 
nerves, therefore, regulate the amount of blood that goes 
to every organ. 

Blushing. — The sudden reddening of the face means 
that more blood is flowing through the skin of the face. 
The arteries by which blood reaches the face have quickly 
widened, and this is because the muscle fibers in the walls 
of the arteries have suddenly relaxed. To go still further 
back in the explanation, some emotion has started nerve 
currents which travel along the fibers of the sympathetic 
nerves and caused the arteries to widen. 

Sudden Pallor. — On the other hand, if the muscle fibers 
in the walls of the arteries suddenly shorten, the face will 
turn pale, because less blood flows in the skin of the face. 
Such a change, as before, is due to the nerve currents 



7 o 



Physiology. 



GRAY ' 
MATTER 



brought by the sympathetic nerves. Of course the face 
may turn pale as the result of the stopping, or checking, 
of the action of the heart, as in ordinary fainting. 

Ordinary Changes in Blood Flow. — Without going to the 
extreme of pallor and blushing, the color of the face varies, 
under the control of the sympathetic nerves. All the or- 
gans of the body receive now more, now less, blood, accord- 
ing as they need it. And all this variation in blood supply 
is regulated by the sympathetic nervous system. 

Effect of Exercise on the Size of the Arteries. — When 
the muscles work, of course they need more blood. To 
give them more blood the ■ +u + . .. 

° SynoDathetic Nerve Chains 

arteries widen. When one 
is exercising actively, the 
muscles take so much blood 
that we should not n , _ 4 

Dorsal Root 

expect the brain or spinal Nerve . 
the digestive organs Ventral Root " 
to do much work, for there 
is only a certain amount of 
blood in the body. Hence if 
one organ, or set of organs, 

getS more blood, the Other Fig- 46. Relation of Spinal Cord and 

Sympathetic Nervous System. 

organs must, for the time, 

receive less. Therefore we see why we should rest after 

eating, both from muscular as well as from mental work. 

How the Heart is made to Beat Faster. — When many 
large muscles are at work, it is not enough merely to widen 
the arteries. This would allow more blood to go to them, 
but would not send them as much as they need. The 
heart must beat faster, or with more force, or both. And 
the heart is made to beat faster and stronger by the nerve 




Control of Circulation. 



7 1 



currents that it receives through the sympathetic nerves. 
When we exercise actively, the fact that the muscles need 
more blood is telegraphed both to 
the heart and to the arteries leading 
to the muscles of the arteries, and 
they are regulated accordingly. 

How the Heart is made to Beat 
Slower. — The slowing of the beat of 
the heart is due to other nerves, not 
belonging to the sympathetic system. 
The vagus nerves are a pair 
of cranial nerves. They arise 
from the sides of the spinal 
bulb, at the base of the brain, 
and, passing downward, give 
branches to the gullet, stomach, 
lungs, and heart. The distri- 
bution of the vagus nerves is 
shown in Fig. 47. Nerve cur- 
rents reaching the heart through the 
vagus nerves make it beat slower, 
and if the current is strong enough, 
as in case of a severe blow over the 
stomach, may, by reflex action, stop 
the heart. 



Lungs 



Heart 



Liver 



Stomach 




Fig. 47. 



Distribution of Vagus 
Nerve. 



Influence of Gravity on Circulation. — Although the heart 
pumps the blood around through the body in spite of 
the force of gravity, yet the circulation is influenced by this 
force. For instance, a person who has fainted should be 
laid flat on his back, that the heart may more easily drive 
blood to the brain. A sore hand feels less pain if held up, 
as in a sling, than when hanging by the side, and a sprained 



72 Physiology. 

ankle does better rested on a chair, as less blood flows to it. 
Nearly every one has noted the pain following the pressure 
of blood when a sore hand, or foot, is suddenly lowered. 

Experiments illustrating the Effect of Gravity on Circulation. — Let 

the pupils stand. Let one arm hang freely by the side. Hold the other 
arm straight up as far as the clothing will readily permit. Observe : — 

1. The difference in the color of the two hands. 

2. The difference in fullness,- both in the feeling of fullness and in 
the projection of the veins. 

3. The difference in temperature; place the backs of the hands 
against the cheeks. 

The position largely regulates the amount of blood in the hand, and 
the amount of blood regulates the temperature, the size, and the color. 

Clothing and Circulation, — No part of the clothing 
should be tight enough to interfere with the circulation. 
Such interference is perhaps most frequent in our foot 
wear. In cold weather tight shoes keep the feet cold 
and may result in their freezing, while the same thickness 
of covering, if loose, would be comfortable. Men often 
wear hats too tight ; this probably leads to baldness. Tight 
garters sometimes hinder circulation and cause cold feet. 

Congestion. — Congestion is an unnatural temporary col- 
lection of blood in any part or organ. This may be merely 
for a short time, and no serious harm results from it. But 
if it is long continued, it may do great harm. 

Inflammation. — If the congestion becomes permanent, 
we call it inflammation. That is, it is a permanent over- 
supply of blood, which may bring many bad results. 
There is usually redness, pain, and often swelling. We 
have all seen such a condition around a boil or a wound. 

Use of Mustard Plaster. — Mustard applied to the skin 
causes irritation. It makes the skin red. This means that 
more blood is drawn into the skin through the action of 



Control of Circulation. 73 

the sympathetic nerves on the muscles in the walls of the 
arteries. If there is more blood in the skin, there must be 
less somewhere else at the same time. Now this is what 
makes a mustard plaster useful. When there is congestion 
or inflammation in some internal organ, a mustard plaster 
applied to the outside draws away some of the blood and 
thus affords relief to the congested part. 

The Hot Foot Bath. — When one has a cold, a hot foot 
bath relaxes the arteries of the feet. This is a good means 
of drawing the blood away from internal organs, and often 
saves the person from serious or even fatal results from 
a bad cold. 

Summary. — i. Circulation is controlled by the nervous system. 

2. This control is involuntary. 

3. The sympathetic nervous system consists of two rows of ganglions 
in the body cavity along each side of the spinal cord. 

4. The sympathetic system regulates the size of the arteries, and by 
this means regulates the amount of blood going to any organ. 

5. The heart may be made to beat faster through the sympathetic 
nervous system. This may come through reflex action and be caused 
by emotions. 

6. The heart may be made to beat slower through the vagus nerves. 

Questions. — i. Why do the feet easily get cold while studying? 

2. What makes the hands grow red and puff up after snowballing? 

3. Why does light exercise before retiring make one sleep better? 

4. How does the application of ice, or cold water, relieve headache? 

5. Why should the clothing be changed after getting wet? 



6 — PHY 



CHAPTER VIII. 
THE BLOOD AND THE LYMPH. 

The Blood. — The blood is composed of a clear liquid, 
the plasma, and the blood cells, or corpuscles. In a drop 
of blood under the microscope tne plasma occupies the 
clear spaces between the corpuscles. The corpuscles 
make up one third of the bulk of the blood, and the 
plasma two thirds. 

Microscopic Examination of the Blood. — To get a drop of blood 
from the finger, wind a cord around the finger, beginning at the base, 
drawing the cord moderately tight, until the last joint is reached. By 
this time the end of the finger is usually well distended with blood. 
With a clean needle make a quick, sharp, light puncture near the base 
of the nail ; this ordinarily brings a drop of blood. Put a very small 
drop on each of several slides and quickly cover with coverslips. 
Examine with a high power. 

The Colored Corpuscles. — These are often called the 
red corpuscles. Although in the mass they give the blood 
a red appearance, when seen singly they are faint yellow- 
ish red. In shape they are seen to be circular disks, 
hollowed on each side like a sunken biscuit. These cor- 
puscles tend to gather side by side, in rolls, like coins. 
Each colored corpuscle is a cell without a nucleus. 

The Colorless Corpuscles. — In the open spaces between 
the rolls of colored corpuscles may occasionally be found 
some spherical corpuscles. They are often called the 
white corpuscles. The colorless corpuscles are very numer- 

74 



The Blood and the Lymph. 



7? 



ous around a wound. They seem to help in repairing 

tissues. 




White Corpuscles 



HIGHLY MAGNIFIED 



White Corpuscle 




Red Corpuscles 
in Rolls 



Fig 48 



MODERATELY MAGNIFIED 
Red and White Corpuscles of the Blood. 



The Plasma. — The plasma consists chiefly of water, 
having in solution various salts, including common salt ; 
it also contains the nourishing materials for the tissues. 
These nourishing materials, obtained from the food by 
digestion, consist chiefly of proteids, fats, and sugar. The 
plasma also contains waste matters from the working tis- 
sues on their way out of the body. 

The Color of Blood. — The difference in color of a single 
corpuscle and the blood in the mass may be better under- 
stood by comparing it with something that we see more 
frequently. A tumbler of currant jelly has a rich, red 



y6 Physiology. 

color, but a thin layer of the same jelly, as when one takes 
a spoonful on a plate, has a pale color, more yellowish. 
The colorless plasma with the colored bodies in it may be 
compared to a glass dish filled with cranberries and water. 

Hemoglobin. — The coloring matter in the blood, then, 
is wholly in the colored corpuscles. Examination of these 
corpuscles shows that their color is due to a substance 
called hemoglobin. The hemoglobin in the corpuscles is 
the chief agent in picking up the oxygen from the air in 
the lungs and carrying it to the tissues in the body. 

The Coagulation of Blood. — When the blood escapes 
from its natural channels it usually changes from a liquid 
to a jelly-like condition. This is known as coagulation. 
It is due to the formation of threads of fibrin from the 
plasma. These threads of fibrin entangle and Jnclose the 
corpuscles, and the two constitute the clot. The liquid 
that afterward separates from the clot is the serum, and 
differs from the plasma only in the absence of the fibrin, 
which is exceedingly small in quantity, though of great 
importance in its action. Coagulation often serves to stop 
the flow of blood from wounds. 

Fibrin. — If freshly drawn blood be stirred rapidly with 
a little roll of wire screen, there will soon collect on the 
wires a stringy substance. Thorough washing will soon 
leave this colorless. It is fibrin. If the stirring has been 
done thoroughly, the blood will no longer clot, no matter 
how long it may stand. 

Watching Coagulation. — If you have a slight cut on the 
hand, it will pay to watch the changes in the blood. First 
it is a red liquid. Then it becomes jelly-like. Then a 
clear or yellowish liquid comes out ; this is serum. The 
serum evaporates and the dried clot forms a scab. 



The Blood and the Lymph. 77 

Liquid Blood and Coagulated Blood. — The following 
scheme shows the difference between the liquid blood and 
the coagulated blood: — 



f ni f Serum 

Plasma ...» 

Liquid Blood \ [ Fibrin 
I Corpuscles 



Clot 



> Coagulated Blood. 



" Black-and-blue " Spots. — A bruise often breaks some 
of the capillaries without breaking the skin. Blood escapes 
into the spaces in the skin or under it. This blood clots, 
and the dark color shows through the skin. This clotted 
blood is gradually absorbed and the color disappears. 

Amount of Blood. — The blood constitutes about one 
thirteenth of the weight of the body. In a body weighing 
one hundred and fifty pounds this would be about six 
quarts. 

Quantity of Blood in Different Organs. — i. One fourth 
is in the heart and the larger arteries and veins (including 
those of the lungs). 

2. One fourth in the liver. 

3. One fourth in the skeletal muscles. 

4. One fourth in the other organs. 

The Lymph Spaces. — We have seen that the capillaries 
have very thin walls. Through their walls part of the 
plasma of the blood soaks out, and is then called lymph. 
It passes into irregular cavities in the tissue called lymph 
spaces. Most of these lymph spaces are minute chinks or 
crevices in the connective tissue of the different parts of 
the body. 

The Lymph Tubes. — Opening out of the lymph spaces 
are irregular passage-ways called lymph capillaries, and 



78 Physiology. 

these lymph capillaries are continuous with larger but 
still thin-walled lymph tubes, called lymph veins. But, 
unlike the blood veins, the lymph veins do not gradually 
increase in size by uniting. They suddenly form a large 
tube, the receptacle of the chyle, beginning in the upper 
part of the abdomen. (See Figs. 50 and 81.) 

The Main Lymph Duct. — This tube soon narrows and 
passes through the diaphragm, close to the spinal column, 
and up along the column near the aorta, and empties into 
the veins of the neck at the junction of the left jugular 
and left subclavian veins. This tube is the " thoracic 
duct," or the main lymph duct. It has numerous valves, 
and, like some of the smaller lymph veins, it presents a 
beaded appearance, due to the filling and bulging out of 
the valves. In the right side of the neck is a short right 
lymph duct, which receives lymph from the right side 
of the head, neck, and thorax, and from the right arm. 
The lymph tubes, as a whole, are usually called the 
" lymphatics." (See Figs. 50 and 81.) 

Valves at the Mouth of the Lymph Tubes. — There are 
valves where these lymph ducts empty into the veins which 
prevent any reflow of liquid into the ducts, but allow the 
lymph to pass freely into the veins. 

Muscle Fibers in the Walls of the Lymph Tubes. — There 
are plain muscle fibers in the walls of the lymph ducts. 

Lymphatic Glands. — In its course the lymph passes 
through many kernel-like masses, the lymphatic glands. 
They may be felt in the armpits, in the groins, and some- 
times in the neck. Lymph contains corpuscles which are 
considered the same as the colorless blood corpuscles. It 



The Blood and the Lymph. 



79 



is thought that these corpuscles are formed in the lymphatic 
glands. In a disease called scrofula the lymphatic glands 
become swollen. (See Figs. 49 and 81.) 

The Flow of Lymph. — The flow of lymph is partly due 
to the blood pressure in the capillaries, this pressure is 
caused by the heart. In our bodies the 
flow of lymph is largely aided by any 
pressure on the lymph veins; for, on 
account of the valves, as in the blood 
veins, any pressure must push the liquid a 
toward the heart. Thus the action of 
the muscles in the limbs, in the chest, 
in the abdomen, in the movements of 
breathing, and in the bending of the WJ/Jllf 

body, etc., all help in this flow, which is 
always very much slower than that in 
the blood veins. 

Relations of Blood Flow and Lymph 
Flow. — While the blood leaves the left 
ventricle by one tube, the aorta, it re- 
turns to the right auricle, not merely 
by the two caval veins, but a part of 
the blood (i.e. of the liquid part of it) 
does not return by blood veins, but hav- 
ing left the blood system proper through 
the thin walls of the capillaries, is 
brought back by the lymph veins, which, 
however, join the blood veins just before 
they empty into the heart. There is 
only one set of distributing tubes, but *%&«*£*££& 
there are two sets of collecting or re- ° f , th : e Arm ; Lyn ]^ 

° Glands at a, b, c, and d 

turning tubes. 



8o 



Physiology. 



The Lymph. — Lymph is a clear liquid. It is more 
watery than the blood plasma, but contains a share of all 



Left Jugular Vein. 

Mouth of 
Lymph Vein-- 
Left Subcla- fc 
vian Vein 




Right Lymph Vein 



.Right Subclavian 
Vein 

, Pre-caval Vein 



Post-caval Vein 



— Main Lymph Vein 

(Thoracic Duct) 



Lymph Capillaries 



Blood Capillaries 



Fig. 50. Diagram of the Circulation of Blood and Lymph (Back View). 



its nourishing substances. Lymph may be defined as 
" diluted blood minus red corpuscles^ The blood proper 
never reaches the tissues. 



The Blood and the Lymph. 



81 



Lymph 



Capillary 



Muscle 
Fiber 



Oxygen 



The Cells of the Body live in Lymph. — The cells of the 
tissues are bathed in .the lymph which fills the spaces in 
the connective tissue (and 
there is connective tissue in 
all the organs of the body), 
as water may fill the spaces 
left between stones built into 
a wall. The cells get all 
their nourishment from the 
lymph, and into the lymph 
they throw all their waste 
matter. 

Importance of Lymph. — 

We can see that the move- 
ment and renewal of lymph 
are as necessary as the circu- 
lation of the blood itself ; is, 
in fact, the most important 
part of it. 

Lymph Cavities or Serous Cavities. — We have noticed 
the pericardial liquid (page 50). There is also a small 
quantity of similar liquid around the lungs in the pleural 
cavities, and in the abdominal cavity, around the digestive 
organs ; also in the cavities of the brain. The liquid in 
each case is lymph, and these cavities, often called serous 
cavities, are lymph cavities. They communicate with the 
lymph tubes. 

Dropsy. — In health the amount of the liquid in these 
cavities is small, but in certain disorders it may accumu- 
late. In general, such affections are called " dropsy." 
The lymph may also accumulate in the tissues of the 
extremities, causing swelling of the limbs called " dropsy.*' 




Fig. 51. Relation of Blood and Muscle. 
(Lymph being Middleman.) 



8 2 Physiology. 

Hypodermic Injections. — When it is desirable that a 
medicine act on the body very quickly, it is sometimes 
introduced under the skin. This is done by means of a 
hypodermic syringe, which is a syringe with a slender, 
needle-shaped nozzle. By means of this the medicine is 
injected into the tissues under the skin. Here it is taken 
up by the lymph and is quickly carried through the system 
and acts on the cells of the body. If the same medicine 
were taken into the stomach, it would require some time 
for it to be absorbed and carried into the tissues. Hence 
time is gained. We can see how much advantage there is 
in this way of giving medicine when the physician wishes 
to stop severe pain. 

The Spleen. — The spleen is a flattish red body at the 
left end of the stomach. There is an active circulation of 
blood in it, and it is supposed to form the colored blood 
corpuscles. It is often called a blood gland. 

Summary. — i . The blood consists of a liquid, the plasma, in which 
float the colored and colorless corpuscles. 

2. The color of blood is given by a substance, called hemoglobin, in 
the colored corpuscles. 

3. When blood is shed it coagulates, tending to check its own 
escape. 

4. Lymph is like the blood diluted and lacking the colored cor- 
puscles. 

5 . A set of lymph tubes conveys the lymph into the veins to join 
the flow toward the heart. 

6. In its course the lymph passes through the lymphatic glands. 

Questions. — 1. What is blood poisoning ? 

2. Which is heavier, blood or water ? 

3. Does it help a sick person to bleed him ? 

4. What is meant by good blood ? Bad blood ? 

5. W T hat is meant by good humored ? Bad humored ? 

6. Does the blood remain the same from day to day ? Or even from 
hour to hour ? 



CHAPTER IX. 
EXTERNAL RESPIRATION. 

The Close Relation between Circulation and Respiration. 

— Is it not a very striking fact that we breathe once for 
every four heart beats? And that whatever quickens the 
breathing also quickens the heart so that the two always 

keep in almost the 
same ratio ? Let us 
try to learn why this 
is so. 

The Organs of Res- 
piration. — i. The 

lungs and air tubes. 
2. The organs which 
increase and dimin- 
ish the size of the 
chest, chief among 
which are the dia- 
phragm and the mus- 
cles acting on the 
ribs. 




Fig. 52. 



Th3 Trachea and Bronchia! Tubes, showing 1 
Two Clusters of Air Sacs. 



External Features 
of the Lungs. — The lungs are of a pinkish color; they are 
very elastic, soft, smooth, and moist. 

The Air Tubes. — The windpipe, or trachea, has in its 
walls rings of gristle or cartilage, which keep the tube 
always open. These rings of cartilage are not complete 

83 



8 4 



Physiology. 




1. Pulmonary Orifice 

2. Aortic Orifice 



Left Aunculo-Ventricular Orifice 
Right Aunculo-Ventricular Orifice 



The heavy black line between the heart and the liver represents the diaphragm. 

Fig. 53. Front View of the Thorax. The Ribs and Breastbone are represented in 
Relation to the Lungs, Heart, and other Internal Organs. 



External Respiration. 85 

rings, but are C-shaped. As the windpipe branches {bron- 
chi) into the two lungs, the cartilages continue in the 
smaller branches which extend into every part of the lungs. 

The Internal Structure of the Lungs. — The lungs are 
full of small cavities, like a loaf of light bread. The small 
cavities are called air sacs or air vesicles, and each air sac 
communicates with the end of one of the branches of an 
air tube, through which air comes into and goes out of 
every air sac. The air sacs are very thin walled, and 
around the sacs are networks of the fine blood tubes called 
capillaries. 

Elastic Tissue in the Lungs. — The air sacs and air tubes 
and their surrounding blood tubes are bound together by 
elastic tissue, which fills up most of the space between them. 

The Mucous Membrane. — The lining of the trachea is 
a mucous membrane. It pours out on its surface a sub- 
stance somewhat 
like white of egg, 
called mucus. This 
keeps the air moist, 
and catches parti- 
cles of dust that are 
in the inspired air. 

t\%. 54. Ciliated Cells lining- the Air Tubes (x 300). -r>i 

There is a constant 
slow current of mucus toward the throat, whence it is, from 
time to time, hawked up. 

Ciliums. — This current of mucus is caused by the cili- 
ums projecting from the lining cells of the trachea. They 
are little hairlike projections, in countless numbers, like a 
field of grass, each cilium having the power of bending 
back and forth, making a quick stroke toward the throat, 
then a slower recover stroke. Thus the united wavelike 




86 



Physiology. 



action of the myriads of lashing ciliurns paddles the mucus 
headward. 

The Pleura. — The outside of each lung is covered by a 
thin membrane, the pleura, which completely surrounds it, 
except at the root of the lung, where the bronchus and 
blood tubes enter. Here the pleura turns toward and 
becomes attached to the inner wall of the chest, forming 
its lining (still called the pleura), and below passes over 



Trachea 



Pleura! Space 

(Exaggerated) 



Chest Wall 




Pleura 



Chest 
" Wall 



D1APHRACM 

Fig- 55. Diagram of the Lungs and Pleuras. 

the upper surface of the diaphragm. The lung is thus 
free, except at its root, where the air and blood tubes 
enter. A very small quantity of liquid moistens the sur- 
faces of the pleuras on the outside of the lung and the 
inside of the chest wall, so they move easily one upon the 
other during respiration. As the lungs are always dis- 
tended enough to fill the chest cavity, these two surfaces 
are always in contact 

Pleurisy. — Pleurisy is an inflammation of the pleura. 
In breathing there is pain from friction or adhesion of the 
pleuras of the lungs and chest wall. 



External Respiration. 



87 



Pneumonia. — Pneumonia is inflammation of the lungs. 
It was formerly called "lung fever." It is due to bacteria. 

The Diaphragm. — The diaphragm is a thin muscle mak- 
ing a complete partition between the abdominal cavity and 
the chest cavity. It is convex above and concave below 
where it fits over the liver and stomach. Its front edge is 
attached to the inside of the chest wall about opposite the 
lower end of the breastbone. Its general position is shown 
in Figs. S3, 55, and 58. 

Triangularis Sterni 
Internal Mammary Vessel's 



Left Phrenic 
Nerve 'V 



Pleura 
Pulmonalis 



Pleura Costalis 




Mediastinum 



( Sympathetic Nerve 
/ Thoracic Duct 



Vena Azygos Major 



Posterior 



Pneumogastric Nerves 
Fig. 56. A Cross-section or the Chest, showing the Heart. Lungs, and Blood Tubes. 

To show the Action of the Diaphragm and Lungs. — Material. — 
Bell jar with stopper, sheet of rubber (such as used by dentists) large 



88 



Physiology. 



enough to covel the mouth of the jar, toy rubber balloon, cork (rubber 
preferred), glass tube, cotton string, collar button. 

Preparation. — Lay the collar button on the center of the sheet of 
rubber, double the rubber over it, stretching the rubber strongly over 
the head of the button, and tie the head firmly in its place. Stretch 
the sheet of rubber over the base of the jar with the base of the 
button on the outside, and fasten with string. Bore a hole in the cork, 
and fix the glass tube snugly in it, so that the lower end of the tube 
will extend about half-way down the jar. Tie the balloon on the lower 
end of the glass tube. 



BRONCHIAL TUBE. 




Fig- 57. Minute Structure of the Lungs, showing Air Sacs and Capillaries. 



Experiment i. — Insert the balloon and tube into the jar, inflate 
the balloon, and while it is inflated tightly cork the jar. If all the parts 
fit well, the balloon should now remain inflated, and the rubber which 
represents the diaphragm will be arched upward. 

Experiment 2. — Pull the diaphragm down, using the base of the 
collar button as a handle. This shows the expansion of the lung by 
the pressure of the external air when more space is given by the 
depression of the diaphragm. On releasing the diaphragm, it springs 
upward, and the balloon becomes smaller, driving out part of the air 
that was in it. This shows how expiration is accomplished, so far as 
the diaphragm is concerned. 

If a bell jar is not at hand, a lamp chimney or a quart bottle may be 
used, after cutting off the bottom, as follows : File a deep notch across 



External Respiration. 



8 9 



near the bottom ; heat an iron rod, and apply the end of it to one end 
of the notch, and slowly draw the rod around to the other end of the 
notch (the rod may need to be reheated). After cracking off the 
bottom oi the jar, hie the edges so they will not cut the rubber. 

Let each pupil make a drawing, showing the position of the parts in 
inspiration and in expiration. 

The Movements of Respiration. — The process of res- 
piration consists of two acts, inspiration and expiration. 




. Increased Air 
Space 




Inspration Expiration 

Fig. 58- Sections of the Body in Inspiration and Expiration. 

Two Active Forces in Inspiration. — In inspiration the 
principal active forces in the body are, first, the dia- 
phragm ; and, second, the muscles which raise the ribs. 

Work of the Diaphragm in Inspiration. — The diaphragm 
is a muscle, and when its fibers shorten, the diaphragm is 
pulled down. In moving down it presses on the abdomi- 
nal organs, and makes the abdomen protrude forward and 
sideways. This lowering of the diaphragm increases the 

7— PHY 



90 Physiology^ 

space in the chest. Air, from the outside, enters through 
the trachea, presses on the inside of the elastic lungs, and 
makes their bases extend, following the diaphragm in its 
descent. The bases of the lungs remain in contact with 
the upper surface of the diaphragm all the time. 

Work of the Chest Walls in Inspiration. — Certain 
muscles of the chest wall raise the ribs and breastbone. 
This widens the chest, and the air, as before, presses in 
through the open windpipe, and keeps the sides of the 
lungs in contact with the inner surfaces of the chest walls. 

Effort required in Depressing the Diaphragm. — Inspira- 
tion requires considerable effort, because the diaphragm 
in its descent presses upon the elastic organs of the 
abdomen (stomach, liver, etc.), and these organs, in turn, 
are pressed against the elastic walls of the abdomen. It is 
somewhat like pressing a pillow down into a rubber bag; 
the pillow springs up as soon as the pressure is stopped, 
because of its own elasticity as well as that of the bag. 
Therefore, as soon as the diaphragm relaxes, the elastic 
walls of the abdomen retreat, and the abdominal organs 
rise to their former place. 

Effort required in Raising the Ribs. — When the ribs are 
elevated, the cartilages which connect the front ends of the 
bony parts of the ribs with the breastbone (see Fig. 6) are 
slightly bent. When the muscles relax, the elasticity of 
the rib cartilages makes the ribs spring back to their 
former position, thus reducing the chest to its former 
width. 

Expiration Easy.- — Thus we see why expiration is easy; 
in fact, "does itself" (in ordinary respiration) by elastic 
reactions. But inspiration is harder than it would be if it 



External Respiration, 91 

were not for the fact that the descent of the diaphragm 

meets resistance, and the ribs, in rising, have to overcome 
resistance in bending the rib cartilages, and in raising the 
weight of the chest walls and shoulders. 

Potential Energy stored in a Door Spring. — When one 
opens a door that has a spring to shut it, he has to use 
more force to open the door than he would if he did not 
have to bend (twist or compress) the spring at the same 
time. But no effort is needed to shut the door. The door 
was opened and shut at the same time ; i.e. when the door 
was opened, force was stored in the spring (in the form of 
what is called potential energy), and this stored energy 
shuts the door while we pass on. We can better afford to 
expend more energy while opening the door than to take 
the extra time to shut it. If, then, a door with such spring 
were fastened open, it might remain open for a long time. 
When released it flies shut. If one, in this case, asks, 
" Who shut the door ? " the answer is, " The person who 
opened it." 

The Storing of Energy during Inspiration. — So in the 

act of inspiration we perform a double work in storing 
energy by which the expiration is performed without active 
muscular effort. 

Review of Forces of Respiration : — 
Forces of Inspiration. 

1 . Depression of the diaphragm. 

2. Muscles elevating the ribs. 

3. Pressure of the external air. 

Resistances to Inspiratio)i. 

1 . Compression of the abdominal organs and stretching abdominal 
walls. 



92 Physiology. 

2. Bending the rib cartilages and lifting the chest. 

3. Stretching the lungs. 

Elastic Reactions of Expiration . 

1. Elastic reaction of the abdominal walls and contents. 

2. Elastic reaction of the rib cartilages. 

3. Elastic reaction of the lungs. 

Forced Respiration. — Thus far we have been speaking 
of ordinary respiration. In forced respiration, as in shout- 
ing, many muscles are brought into play to expel the air 
rapidly and forcibly. In such an act as coughing there is 
vigorous action of the abdominal muscles. 

Abdominal and Thoracic Respiration. — The main part of 
respiration is performed by the diaphragm, and is there- 
fore called diaphragmatic or abdominal breathing. Breath- 
ing by means of the chest walls is called thoracic, or costal 
breathing. 

The Rate of Respiration. — Adults breathe about seven- 
teen or eighteen times a minute, or about one breath to 
four heart beats. The rate is increased by exercise, tem- 
perature, digestion, excitement, age, etc. 

Special Forms of Breathing, — Coughing is a forcible 
expiration, usually directed through the mouth, and for the 
purpose of getting rid of some irritating substance. In 
sneezing there is first a deep inspiration, and then the air 
is forced out, chiefly through the nose. Sneezing may be 
prevented by pressing firmly on the upper lip. Hiccuping 
is sudden inspiration, produced by a jerky action of the 
diaphragm, accompanied by a sudden closing of the en- 
trance to the windpipe. In case of choking it is well to 
hold the head well forward, and perhaps downward. A 
smart slap between the shoulders sometimes helps dislodge 



External Respiration. 



93 



anything stuck in the throat, and it may be necessary to 
hold a child with the head downward. There are various 



-S u - 



to § 

CO 







COMPLEMENT AL AIR. 










120 CUBIC 


INCHES. 






AIR 


THAT 


CAN BE BUT 


SELDOM IS 


TAKEN 


IN. 


TIDAL AIR.— 20 to 30 C 

and Sent out at 


jbic Inches 
Each Breai 


Air Taken in 
'h. 






RESERVE AIR. 










100 CUBIC 


INCHES. 






AIR 


THAT 


CAN BE BUT IS SELDOM 


DRIVEN 


OUT. 






RESIDUAL AIR. 










100 CUBIC 


INCHES. 








AIR 


THAT CANNOT 


BE DRIVEN OUT. 





&3 



Fig. 59. Diagram of Lung Capacity. 



other peculiar forms of respiration, such as yawning, sniff- 
ing, laughing, etc., which you can explain after watching 
and thinking about them. 



94 Physiology. 

Capacity of the Lungs. — Have the class stand, and each 
pupil raise his right hand. 

i . Tidal Air. — Let all breathe together, at the ordinary rate and 
depth, and let the hand rise about three inches during inspiration, and 
fall again during expiration. The amount of air taken in at an ordinary 
breath is from 20 to 30 cubic inches, or about a pint. This is called 
tidal air. 

2. Complemental Air. — As before, let the hand go up and down 
with the breathing, but at the end of the third inspiration, instead of 
stopping with the usual amount, keep on breathing in as much as pos- 
sible, letting the hand rise accordingly. This air that can be taken in 

'above the ordinary breath is called the complemental air, and it is 
estimated to be, on the average, about 120 cubic inches. 

3. Reserve Air. — Begin as before, and at what would be the end 
of the third expiration continue to drive out as much air as possible, 
indicating the degree by lowering the hand. This air that can be 
breathed out beyond the ordinary expiration is called the reserve air, 
and is reckoned at about 100 cubic inches. 

4. Residual Air. — The air cannot all be breathed out. The re- 
mainder is called the residual air, and is computed to be about 100 
cubic inches. 

The Vital Capacity. — All the air that can be breathed out after a 
full inspiration, i.e. the sum of the complemental, tidal, and reserve 
air, would be about 240 to 250 cubic inches, and is called the vital 
capacity. Of course these figures represent only the average of cer- 
tain experiments and observations. By practice any one can consid- 
erably increase his vital capacity. 

A Test of the Capacity of the Lungs. — A simple method of measur- 
ing these stages of respiration is to take a gallon bottle and first care- 
fully graduate it to pints by pouring in water and marking on the 
outside with a file. Then fill the bottle with water, invert it in a trough 
of water, and exhale into it by means of a rubber tube. 

Hygiene of Breathing. — Those persons who take con- 
stant exercise in the open air are not likely to suffer much 
from deficient respiration. But persons who lead an indoor 



External Respiration. 95 

life, especially those who are sitting much of the time, need 
to pay especial attention to the matter. 

The Nasal Passages. — The nasal passages are fitted for 
the introduction of the air (1) by being narrow, but of 
large area; (2) by having their lining membranes richly 
supplied with blood; (3) by the abundant secretion of 
mucus by this membrane. The air, coming through this 
narrow channel, is warmed, and a large part of any dust 
it may contain is caught by the sticky mucus that covers 
all the walls of this passage-way. 

Adenoids. — When any person breathes through the 
mouth, there is something wrong somewhere in the nasal 
passages. Children who breathe through the mouth and 
" snore" at night generally have a growth of gland-like 
tissue called " adenoids " at the back part of the nose and 
behind the palate. Not only is breathing through the 
mouth bad because it allows cold air and dust to go down 
into the windpipe, but the mouth breather cannot get 
enough air properly to aerate his blood. Mouth-breathing 
children, therefore, are frequently peevish and not dis- 
posed to play. They do not sleep or eat well, are apt to 
be croupy, and are more liable than nose-breathing chil- 
dren to contract diseases like diphtheria and croup. Such 
children should be taken to the doctor and the adenoids 
should be removed. 

Deep Breathing. — It is a grateful relief to the whole 
system to stand, stretch, inhale deeply and slowly several 
times, and to repeat this every hour or so. Every one 
engaged in office work or studying should form this habit, 
especially if he does not give an hour daily to exercise. 

Control of Respiration. — Breathing is an involuntary 

action. It is under the control of the nervous system, and, 



96 Physiology. 

without attention on our part, it goes on, varying in rate 
according to the needs of the body. About every fifth 
breath is a little deeper than the others, and if we are sit- 
ting in a cramped position, or are depressed, this occasional 
deeper breath is still more marked and is called a sigh. 
If the tissues are not well supplied with oxygen, they make 
it known to nerve centers through the nerves, and, by 
reflex action, breathing is quickened. 

Summary. — 1. In the lungs the air and blood are brought very close 
together, only the wall of the capillary and that of the air vesicle being 
between them. 

2. Through these two layers oxygen passes from the air sac into the 
blood. Carbon dioxid, water vapor, and other wastes pass from the 
blood into the air sac. 

3. The mucous membrane of the air passages secretes mucus which 
is driven toward the nostrils by the ciliums. 

4. The chest is lengthened by the lowering of the diaphragm, and 
widened by the lifting of the ribs, giving greater space, which is filled 
by external air expanding the lungs. 

5. Inspiration requires extra effort; but ordinary expiration is with- 
out effort because of the elastic reactions. 

6. Forced expiration, as coughing, requires active muscular effort. 

7. The vital capacity may be increased by practice and by exercise. 

8. We should breathe through the nose, not through the mouth. 

9. Respiration is under the control of the nervous system. 

Questions. — 1. Is it well to see how long one can hold his breath ? 

2. Should the head be covered by bedclothes ? 

3. How is respiration affected by a stooping posture ? 

4. What are the " lights 11 of an animal ? 

5. Of what advantage is it that the cartilages of the windpipe are 
C-shaped, and not complete rings ? 

6. From the statements in this chapter of the amount of air taken in 
at each breath and of the rate of breathing, find out how much air is 
breathed in an hour. How much in twenty-four hours ? 



CHAPTER X. 

INTERNAL RESPIRATION. 

Composition of the Air. — Air has about 20 per cent oxy- 
gen and 80 per cent nitrogen, or one fifth oxygen and four 
fifths nitrogen. There is a very small amount of carbon 
dioxid, and usually there are traces of other gases. 

Experiments illustrating Internal Respiration. — Material Neces- 
sary. — A piece of candle an inch or two long, two tumblers, a tube 
eight inches long (a straw will serve), a nail, and lime water. The lime 
water should be prepared the day before by putting a piece of fresh 
quicklime as big as a hen's egg in a quart of water. The next morning 
carefully pour off the clear water for use in experiment. 

Experiment i. — Light the candle and hold a cold tumbler inverted 
a little above it. The moisture that dims the inside of the tumbler is 
water that has been produced by the burning of the candle. The oxv- 
gen of the air unites with something in the candle and forms water. 

Experiment 2. — Breathe into a cold tumbler. The tumbler is 
dimmed by the water in the air we breathe out. 

Experiment 3. — Lower a tumbler over the burning candle till the 
tumbler rests on the table. Observe that the flame is soon put out. 
Carefully lift the tumbler and slip one hand under it so that the palm 
tightly covers the mouth of the tumbler. Invert the tumbler. Lift one 
edge of the hand and pour in about two tablespoonfuls of lime water. 
Thoroughly shake the tumbler, keeping it tightly closed. The lime 
water is turned milky by the carbon dioxid produced by the burning 
candle. There is carbon in the material of the candle, and the union of 
oxygen with this carbon produces carbon dioxid. 

Experiment 4. — Pour about two tablespoonfuls of lime water into 
a tumbler and breathe through it by means of a tube. The lime water 
is turned milky by the carbon dioxid in the breath. There is carbon in 

97 



98 Physiology, 

the tissues of the body. Oxygen unites with this carbon, forming car- 
bon dioxid. We know that there is carbon in beef, for when it is over- 
baked we see the black carbon where it is charred. There is carbon in 
our muscles and in all the other tissues. 

Experiment 5. — Place a nail, or any piece of iron, in a tumbler of 
water. It will soon rust. Rusting is caused by the union of oxygen 
with the iron. When anything unites with oxygen it is said to oxidize. 
When the union is rapid, as with the burning candle, it is called com- 
bustion. 

Experiment 6. — Hold a thermometer at arm's length. It shows 
the temperature of the air, — of the air you are breathing in. Breathe 
for a few minutes upon the bulb of the thermometer and you have proof 
that the air we breathe out is warmer than the air we breathe in. 

How the Body is like a Candle. — The burning candle 
and the body both produce heat. To do this each must 
have oxygen. The oxygen unites with carbon and other 
elements in each, and produces carbon dioxid, water, and 
other substances. And just as a candle flame is soon put 
out in a closed tumbler, so life would be destroyed by suf- 
focation if an animal were shut in an air-tight room. 

Exchanges between the Air and the Blood in the Lungs. — 

Whatever the air coming from the lungs contains that was 
not in the air entering them it has taken from the blood, 
and what the air has lost it has given to the blood. The 
air in the air vesicle is separated -from the blood in the 
pulmonary capillaries only by the thin wall of the air vesicle 
and the thin capillary wall. 

What the Air gets from the Blood. — Carbon dioxid, water, 
and other waste matters pass from the blood through this 
thin partition into the air vesicle, to be sent out by later 
expiration through the bronchial tubes and windpipe. The 
air also gets heat from the blood (see Fig. 60)0 



Internal Respiration. 



99 



What the Blood gets from the Air. — Oxygen from the air 
in the vesicle passes through these layers into the plasma, 
and most of it is quickly picked up by the colored corpus- 
cles. The colored corpuscles are the carriers of oxygen. 



BRONCHIAL TUBE 



FROM PULMONARY ARTERY 



TO PULMONARY VEIN 




CORPUSCLES 

capillar 

Fig. 60. Exchanges between the Air and the Blood in the Lungs. 

Hemoglobin and Oxy-hemoglobin. — The hemoglobin in 
the colored corpuscles is eager to unite with oxygen. 
Hemoglobin is of a dark color, and gives the dark color 
to the blood which enters the lungs. When oxygen unites 
with the hemoglobin it forms oxy-hemoglobin, which is of a 
bright red color. Hence the change in the color of the blood 



IOO 



Physiology. 



in the lungs from a dark bluish red to a bright scarlet. 
This bright blood is usually called "arterial/' and the dark 
"venous"; but it must be remembered that the blood in 
the pulmonary artery is dark, and in the pulmonary veins 
bright. 



rfXM^e 




Fig. 61. Circulation in the Capillaries of the Lungs and in the Capillaries of the Body. 

The Changes in the Blood. — What does the blood do 
with the oxygen that it gets in the lungs, and where did it 
get the carbon dioxid and other impurities that it brings to 
the lungs ? Let us follow the blood and see. From the 
pulmonary veins the blood goes to the left heart, and is 
pumped to all the tissues except the lungs. Let us follow 
a branch of the aorta that leads to a muscle. 

The Production of Heat and Motion in the Body. — When 
a muscle works it becomes warmer. The rise in tempera- 
ture has been repeatedly proved by experiment. We know 
that the blood is flowing more rapidly through the muscle 



Internal Respiration. 101 

when it is at work. The more rapid stream brings the 
muscle more oxygen. This it needs, for it is by the oxida- 
tion of the muscle (or substance in it) that the muscle 
produces heat and motion. The oxidation in our tissues is 
a slow oxidation, more like the rusting of iron than the 
burning of a candle. Oxidation in our bodies never pro- 
duces a high degree of heat and never produces light. 

Increased Blood Flow is the Result of Exercise. — When 
we exercise, the muscles need more oxygen. They also 
need to have removed the waste matters that they are so 
rapidly producing at this time. How is the oxygen brought 
and the waste removed ? By the blood, you answer. True ; 
but what makes the blood come and go faster at this time ? 
By reflex action, you reply. The muscles send a message 
to a nerve center, and this nerve center sends back a mes- 
sage to the blood tubes, making them widen, and the heart 
also may be made to beat faster. 

Increased Respiration from Exercise. — But would it do 
any good to have the blood flow through the muscles faster, 
if it could not bring more oxygen, and take away and get 
rid of more wastes ? You will say no. To give the extra 
oxygen and take out the carbon dioxid, the lungs cannot, 
of themselves, take in and send out air. The work of 
pumping air depends on the muscles of respiration, the 
diaphragm, and the muscles that elevate the ribs. These 
muscles will not work faster unless they are ordered to do 
so. A message must be sent to them telling of the need. 
Thus, by a series of reflex actions, all these processes are 
kept in close relation to each other. It must be borne in 
mind that increased blood flow is the result, and not the 
cause, of the increased activity of the tissues. 

Temperature of the Body. — Insert the bulb of a thermometer into 
the mouth, and keep it there three or four minutes to find the tempera- 



102 Physiology. 

ture of the inside of the body. For this it is better to use a clinical 
thermometer, if one can be obtained. The average temperature of the 
tissues within the body is about 98.5 F. 

How the Body is like a Stove. — The body may be com- 
pared to a stove. Into one we put fuel and produce heat, 
In the other we get heat from food- Both take in oxygen. 
Both produce carbon dioxid, water, and other waste matter. 

How the Body differs from a Stove. — But the body is not 
like the stove in burning the fuel (food) directly. The 
food is first made into tissues, or material stored in the 
tissues. It is as though we were to build a stove entirely 
of coal, and then start a fire in it. In that case it would 
produce heat not merely by burning in one place within, 
but would be burning throughout the whole of its sub- 
stance. This is the case with the body. 

Oxidation in Tissue the Source of Heat in the Body. — 

The muscles make up nearly half of the weight of the 
body. They are more active than most of the tissues. 
We would naturally infer, as is the fact, that they are the 
chief source of the heat produced in our bodies. The 
tissues of the body are oxidizing all the time. But when 
in vigorous action they oxidize very much more rapidly. 

Production of Heat in the Liver. — Next to the muscles, 
in importance as a heat producer, is the liver, which is the 
largest gland in the body, and, as we shall soon see, one of 
the most active. The blood, as it leaves the liver by the 
hepatic vein, is hotter than anywhere else in the body. 

How the Body is like a Locomotive. — But it will be better 
to compare the body to a locomotive, as we produce not 
only heat, but motion:— 1. Both are warm; 2. Both 
move ; 3. Both use fuel (food or coal) ; 4. Both take in 



Internal Respiration. 103 

air. 5. Both give off gases, consisting mainly of carbon 
dioxid and water vapor. 

How the Body differs from a Locomotive : — 1. The body 
does not get hot enough to burn ; i.e. the oxidation is 
relatively slow, and is not combustion. 2. The oxidation 
of the body never produces light. 3. The oxidation in the 
body is always in the presence of moisture. 

The Amount of Carbon Dioxid given off. — When the 
breath is held for some time, the carbon dioxid in the 
expired air may reach 7 or 8 per cent. During violent 
exercise the amount of carbon dioxid given off may be 
more than twice as much as when we are at rest. In 
ordinary respiration there is one hundred times as much 
carbon dioxid in the air we breathe out as there was when 
it was taken in. Oxygen is carried chiefly in the cor- 
puscles, but the carbon dioxid is carried in both plasma 
and corpuscles. 

Effect of Re-breathing Air. — Every one knows how 
unpleasant it is to breathe the air of a close room where 
many people are present. In many persons such air 
causes headache and drowsiness. This effect is not due 
to the reduced amount of oxygen, nor is it due to the 
increase of carbon dioxid. It is believed to be due to 
the " organic impurities" which are thrown out in the 
expired breath. It is this matter that gives the offensive 
odor to a room which is kept close and warm after a crowd 
has been in it. If in a crowded lecture room you divide 
the space by the number of people present, you find that 
each one has really very little room. In such rooms 
special attention to ventilation is necessary, or great injury 
will be done. When we learn how many cases of lung 



104 Physiology. 

diseases are found wherever people are crowded into ill- 
ventilated rooms, we can realize the force of the statement, 
" Man's own breath is his worst enemy." 

Summary of Respiration. — The tissues need oxygen ; 
air is pumped into the lungs; this air gives oxygen to the 
blood ; the blood carries it to the tissues. 

In oxidizing, the tissues produce energy (heat and 
motion) and give off waste matter (water, carbon dioxid, 
etc.); these the blood carries to the lungs, the lungs give 
them to the air, and the air carries them out of the body. 

The pumping of the air in and out and the exchanges 
between the air and the blood in the lungs may be called 
"external, or mechanical respiration." The action of the 
oxygen of the blood in the tissues is the " real, or internal 
respiration." 

Summary. — I. In passing through the lungs air loses oxygen, and 
gains water, carbon dioxid, and other wastes. 

2. Oxygen is carried chiefly by the colored corpuscles of the blood ; 
it unites with hemoglobin in the corpuscles, forming oxyhemoglobin, 
and gives the blood its bright scarlet color. 

3. The energy of heat and motion in the body results from the 
oxidations in the tissues. 

4. Air once breathed is unwholesome. The air of living and sleep- 
ing rooms needs constant renewal. 

5. When we exercise more, the muscles need more oxygen, so the 
heart must beat faster and we must breathe faster. 

6. The body is like a locomotive in producing heat and motion by 
oxidation. 

7. Air, once breathed, has one hundred times as much carbon 
dioxid as before. 

Questions. — 1. In what part of the lungs is the best air? Where 
the worst? 

2. Is it easy to determine by the color of blood flowing from a 
wound whether it is arterial or venous? Why? 



Internal Respiration. 105 

3. How is the air of a room affected by having many lamps or gas 
jets burning ? 

4. How is air affected by gasolene or kerosene stoves ? 

5. Could a locomotive be run by feeding it with bread and meat ? 



8 — PHY 



CHAPTER XL 

VENTILATION AND HEATING. 

Need of Proper Ventilation. — When one is actively 
exercising he may keep warm outdoors even on a cold 
winter day. For the heat of the body depends on its 
internal fires, the oxidation of its tissues. But if we are 
inactive, these fires burn feebly, and we need outside heat. 
While air is free, it really costs a good deal of money to 
have it properly warmed. 

A Lack of Effective Systems of Ventilation. — Lung 
diseases are rare in the regions where the windows and 
doors may be kept open most of the days of the year. It 
is from shutting ourselves in so closely that we suffer. 
This is especially true where many people are housed in a 
comparatively small space, as in many public buildings. 
But in our private dwellings, even when the owners are 
amply able to secure the best appliances, defective Appa- 
ratus is often put in. Any system that does not provide for 
a constant renezval of the air is defective. 

The General Principles of Ventilation. — Of the forces 
that renew the air of rooms two are natural, (i) diffusion 
and (2) the wind ; and two are artificial, (3) warm air shafts 
and (4) fan systems. 

Diffusion. — Gases tend to mix. We know that if a 
bottle containing an odorous substance is opened in a 
room where there are no air currents the odor tends to 

106 



Ventilation and Heating. 107 

spread equally through the room. If a person is in one 
corner of a large room, where there are no inlets or out- 
lets, and no currents, as he uses the oxygen immediately 
around him, the oxygen farther away will diffuse toward 
him so that he will continue to get oxygen as long as there 
is any in the room. So, too, the gases that he breathes 
out will not remain confined to the space directly about 
him, but will spread nearly evenly throughout the room. 
The same takes place in the open air, without wind. So, 
then, if the windows and doors are open, the air of the 
room will be renewed by diffusion. 

Wind. — Motion of the air renews faster than mere dif- 
fusion. Strong wind forces its way through the cracks 
around windows, and when windows are open on opposite 
sides of a room there is usually enough breeze to renew 
the air. But during part of the year this cannot be done. 

Artificial Renewal of the Air. — The renewal of the air 
in most cases depends on the fact that heated air rises. 
Heat expands air. It is then lighter, bulk for bulk, than 
cooler air. The heavier surrounding air presses the lighter 
air upward. If there are outlets above and below, the 
heavier, colder air will press in below, and push the lighter, 
warmer air out above. 

Grates as Heaters. — Grates are the simplest and prob- 
ably the earliest form of heater. The fire throws out heat 
in straight lines, or as we say, radiates heat into the room. 
So much of the heat goes directly up the chimney that a 
grate is very wasteful of fuel. 

Grates as Ventilators. — But a grate is an excellent ven- 
tilator. There is always a decided draft toward a grate 
fire. This means a constant renewal of air. The air 



108 Physiology. 

pushing toward the grate may be cold, and this has disad- 
vantages that are hard to overcome in cold weather if there 
is no other way of supplying heat. But it is a serious 
question whether, with all our modern improvements in 
heating, we have better air in our houses, or take cold less 
often than our grandfathers, even if they did " roast on 
one side while they froze on the other." 

Stoves as Heaters. — A stove is a very much more effec- 
tive heater than a grate. In the first place the stove gives 
off heat on all sides. In the second place a good deal of 
heat is given off by the stovepipe; while in the grate 
almost no heat is saved from the flame and smoke. 
Again, the fire can be better regulated in the stove. 

Air Currents produced by Stoves. — There is always a 
current of heated air rising above a hot stove. Children 
make whirligigs and other toys to place in these up-currents. 
When this heated air reaches the ceiling it passes along 
the ceiling, and comes down along the walls in the colder 
parts of the room. At the same time colder air is flowing 
along the floor toward the stove. This, in turn, is heated 
and rises, making a constant circuit, along the floor to the 
stove, up from the stove to the ceiling, along the ceiling 
to the walls, and down the walls to its starting-point, again 
to repeat the round. 

Stoves as Ventilators. — If there is an opening at the 
top of the room, heated air will escape through it. Often 
the heat is used to warm upstairs rooms in this way. If 
a window is open at the top, some heat is lost. To make 
up for the losses above named, and also for the air that 
enters the stove and goes up the chimney, more air is 
drawn in usually around doors and windows. It is espe- 
cially noticeable where there are openings near the floor. 



Ventilation and Heating. 



109 



For the cold air is heavier than the warm air and continu- 
ally pushes the warm air up and out of the room wherever 
it can. But the stove does not send as much air up the 
chimney as the grate does, and so does not draw in as 
much fresh air. It is therefore not a good ventilator. 
But the stove gets much more heat from a given amount 
of fuel. 

A Stove and Jacket. — In some cases a jacket is placed 
around a stove, and a duct from the outer air connects 




Fig. 62. The Unjacketed Stove 



with the lower part of the space inside of the jacket and 
outside of the stove. Then as the air heated by the stove 
rises, fresh air is drawn in from outside to be warmed. 
In this case the direct heat from the stove is shut off from 
the room. Heat radiates in straight lines. When one 
holds out his hands beside a stove, the heat he receives 
is radiant heat. Most of the heat from a grate is radiant 
heat. But in a jacketed stove the heating by air currents 
is called heating by convection. 



no Physiology. 

The Furnace. — A furnace is practically a jacket stove 
placed in a basement. Hot-air furnaces have this good 
feature, that they are all the time sending fresh air 
into a room. The main trouble is, the air is usually too 
dry. There should be in the furnace a pan of water to 
furnish moisture to the air. 

Foul-air Shafts and Fans. — Although in private dwell- 
ings heated by furnaces there is no special provision for 
the escape of foul air, there is ordinarily sufficient renewal 
of the air. But in public buildings there should be escape 
flues for foul air. Frequently a large foul-air shaft is built 
near the center of the building, and a small stove placed 
in it to create a sufficient up-current. In many public 
buildings the currents created by heat are not strong 
enough to renew the air properly. Revolving fans are 
used, which force the air, properly heated, into the room. 

Direct Heating. — In heating by steam or hot water, if 
the radiators are placed in the room they give direct or 
radiant heat. This system is called direct heating. It 
gives direct heat, and produces air currents within the 
room. In itself it has no provision for renewing the air. 

Indirect Heating. — In indirect heating, coils of steam 
or hot-water pipes are placed in air shafts which lead up 
to the rooms above, and also- have ducts to the outside. 
As the air is heated by the heat of the pipes it rises into 
the rooms above, and fresh, cold air presses in through 
the ducts, to be, in turn, heated and sent up. If there is 
at the same time a proper escape for the foul air, this 
makes an excellent system. 

A Combination of Direct and Indirect Heating. — It is a 
good plan to combine direct and indirect heating. Where 



Ventilation and Heating. i 1 1 

there is a grate in a room, it serves very well as a foul-air 
shaft, especially when there is a fire in the grate. It is 
well to have the flue from the grate in the same chimney 
with that from the smoke-pipe from the furnace, as then the 
heat from the smoke will cause a constant up-draft in the 
grate flue, whether there is a fire going in the grate or not. 

With a grate, in private houses, there is ordinarily no 
need of other foul-air shaft for any room. But it is very 
desirable to have at least some " indirect " heat, so that 
the fresh air introduced will be sufficiently heated. 

If the introduction of air is thus provided for, it is then 
safe to put on double windows and make the cracks around 
the door very tight. Without any special provision for the 
renewal of the air these cracks are the means of safety. In 
houses heated by furnaces, steam, or hot water, the floor 
is likely to be warmer from the escape of heat from the 
heater itself, and from pipes or air ducts under the floor. 

Double Windows. — There is a very common misunder- 
standing as to the cold felt near a window in cold weather. 
It seems that air is entering; but a little reflection will 
show that even if the window were air-tight this effect 
would be produced, for the air near the window is cooled 
by losing heat to the outer air through the glass. The air 
next to the window, thus cooled, is heavier, and falls to the 
floor ; and if there is any source of heat in the room, this 
cold air will pass along the floor to that source of heat, up 
from the heating body to the ceiling, and across the ceil- 
ing, and so on around again. There may thus be currents 
without any change in the quality of the air. It is 
economy to use double windows and prevent the loss of 
heat through the glass. So both economy and comfort 
suggest to us that we reduce as much as possible cracks 
around doors and windows, use double windows, make 



112 Physiology. 

vestibules at entrances, and build special ducts by which 
fresh air may enter, and heat it properly on its way in. 

To Air a Room without Draft. — To introduce fresh air 
into a room without having a draft, a good plan is to get a 
board four inches wide and as long as the width of the 
window sash. Raise the window, place the board under 
it and shut the window down upon the board. This will 
allow air to enter between the upper and lower sash, and 
it will be directed toward the ceiling. This is of double 
advantage; in the first place, it does not strike any one 
directly ; in the second place, it mingles with the warm air 
of the upper part of the room before it reaches us. 

Wearing Slippers. — In rooms heated by stoves or grates 
there is always more or less cold air moving along the 
floor. Wearing slippers in such a room causes many per- 
sons to take cold. The ankles have been warmly dressed 
through the day and while the person was more active. 
Especially if one is studying there is a tendency to draw 
the blood away from the feet and make them cold. It is 
restful, in the evening, to take off the shoes that have been 
worn during the day; but, for most persons, it would be 
better to put on a pair of loose shoes so the ankles will be 
protected. The floor is usually the coolest place in a room. 
In sitting in a room heated by a grate, or stove, the head 
usually gets the most heat, and the feet the most cold, just 
the reverse of what it should be. If much heat escapes 
from a furnace, the floor may be warm. Those who use 
stove heat in loosely built houses, learn to keep the feet up 
on a stool when sitting in a room in cold weather. 

Ventilation of Cellars. — The cellar is the source of con- 
tamination of the air of many houses. Of course a cellar 



Ventilation and Heating. I t 3 

ought to be dry, well lighted, and well ventilated. But 
since many of them are dark and ill ventilated, especial 
care should be taken to keep them dry. Fruit and vege- 
tables should not be allowed to decay in the cellar. On 
entering many houses one can at once detect the smell 
of decaying potatoes and other vegetables. Such material 
should be promptly removed. The best time to ventilate 
a cellar is at night, for if the cellar windows are opened 
in the day time, the entering air will deposit moisture, 
making the cellar more damp instead of dryer. 

Summary. — i. Lung diseases usually accompany close confinement, 
but are rare with those living in the open air. 

2. Air in rooms needs constant renewal. 

3. Grates are good ventilators, but not economical heaters. 

4. Stoves are economical heaters, but poor ventilators. Both grates 
and stoves heat very unevenly. 

5. All crowded rooms, as schoolrooms and churches, need special 
inlets for fresh air and outlets for foul air. 

6. The most common means of withdrawing the air is by foul-air 
shafts. Heat is the force relied on, but the removal of foul air is usually 
inadequate, on account of the slowness of the current or the narrowness 
of the outlet, or both combined. 

7. Fans are much more certain to be effectual . 

8. Steam and hot water may heat directly (by radiation) or indirectly 
(placed in flues). It is best to combine direct and indirect heating. 

Questions. — i . How can we renew the air of a room without having 
unpleasant drafts? 

2. Should bedroom windows be open at night? Is night air bad? 

3. What dangers in the use of hard coal ? 

4. Should there be a damper in the smoke-pipe of a hard coal stove? 

5. What do miners mean by u choke damp " ? 

6. Compare stove and furnace heating. 

7. Compare heating by steam and by hot water. 

8. Read about the " Black Hole of Calcutta. 7 ' 



CHAPTER XII. 

DUST AND BACTERIA. 

The Air is washed by Rain or Snow. — Every one will 
recall how delightfully refreshing the air is after a rain or 
a snowstorm. This is not due merely to the fact that the 
air is cool. It is clean because it has been washed. The 
rain and snow absorb most of the various impure gases 
that are in the air. The raindrops and snowflakes also 
bring down with them many particles of dust that were 
floating in the air. Take some of the snow that has fallen 
in a town. It looks pure in its almost dazzling whiteness, 
But melt some of it, and you will usually find that the 
water has an inky tinge, showing that as the flakes sifted 
down through the air they caught myriads of particles of 
dust. 

The Sources of Dust. — Where soft coal is used to any 
large extent it is one abundant source of this dust. In 
summer dust has many sources. The dust that blows into 
your face, and perhaps into your mouth, may be made of 
dry soil. Take a dry clod and drop it ; it falls quickly to 
the ground. Crush it in your hand before dropping it, and 
much of it floats in the air for some time. Any substance 
that is easily dried and reduced to powder may form part 
of the common dust. The dust that you wipe from your 
eye, or is caught by the mucus of the nasal, passages, may, 
instead of being made of clean soil, be from the excreta of 
horses, decayed leaves, wood, grass, etc. Indoors we are 

114 



Dust and Bacteria, i i 5 

constantly making dust by wearing out our clothes. Many 
of the tiny particles that we see floating in the sunbeams 
are bits of cotton or woolen fibers. Shake any garment in 
a beam of light to see how much dust is given off. The 
worn-off particles of our shoes, books, floors, all contribute 
to the ever-present dust. 

The Effect of Dust on the Lungs. — This dust is irritating 
to the lungs and respiratory passages. There is provision, 
as we have seen, for catching and getting rid of a good 
deal of it. But still much is taken into the lungs. Exam- 
ination shows that the lungs have many black specks from 
particles of carbon, etc., that have become lodged, and are 
of no benefit, to say the least. 

Composition of Live Dust. — Bad as this dead dust is, the 
injury from it is slight compared to that from live dust. 
We know that certain seeds float in the air, carried along 
by the wind. But these are comparatively heavy, and soon 
sink to the ground. 

We all know pollen. At certain seasons it forms, in the 
vicinity of cornfields, for instance, a considerable part of 
the dust. This is alive. It will grow if it falls on the 
stigma of the right plant at the right time. Such dust will 
not grow in our bodies. We do not furnish a soil in which 
it can grow. It merely adds to the amount of irritating 
dust. 

Puffballs and Molds. — We have seen puffballs give off 
a cloud of dust when they are crushed. So, too, from a 
patch of mold, when brushed, we often see a little cloud of 
dust. This dust is composed of live spores that will grow 
in suitable places and conditions. 

Yeast. — If we set a tumbler of cider on a table in a 
warm room, in a few days it ferments. This is due to 



1 1 6 Physiology^ 

a kind of living germ or spore that has gotten into it from 
the dust on the fruit before it was crushed, or from dust 
in the room. Boil the cider to kill the spores already in 
it, and cork it securely so that air cannot get at it, and it 
will not ferment. These are a few instances of kinds of 
living dust that do not affect human beings any more 
than so much dead matter. 

Disease Germs. — But there are floating in the air many 
kinds of spores that may grow in our bodies. We know 
that many of our contagious diseases are due to the growth 
of some of these spores in our bodies. Our bodies are a 
good soil for certain germs. The germs that cause con- 
sumption, typhoid fever, Asiatic cholera, erysipelas, diph- 
theria, lockjaw, the grippe, malaria, yellow fever, and blood 
poisoning are well known. Microscopists know them when 
they see them as readily as we know peas from beans. 
And it is proved beyond all doubt that these germs get 
into our bodies by being breathed in, or by being eaten in 
food, or in drinking water, or by introduction into the 
blood in wounds. We have reason to believe that small- 
pox, measles, mumps, whooping-cough, and scarlatina are 
caused by germs, but these diseases have not been studied 
so successfully. 

How to avoid Germs. — How can we avoid or get rid 
of dusts of these kinds ? To exterminate any plant, we 
try to keep the seeds from ripening, and to kill all that do 
ripen. Let us take a case that, while not pleasant to think 
about, is too terribly true to allow of being called an imag- 
ined case. 

The Danger from Consumption. — A consumptive spits 
on the pavement. In this sputum are probably hundreds, 
if not thousands, of germs known as bacilli {Bacillus tuber- 



Dust and Bacteria. 



117 



miosis). They are alive. Now, so long as they remain 
on the pavement they do no harm. The sputum dries. 
But the bacilli are not killed by drying. With other dry 
material from the pavement they form part of the common 
dust. Any one of us may breathe some of this kind of mat- 
ter any day, for there are persons afflicted with this dreaded 



S** 







Bacillus of Diphtheria (x 1000) 






Bacillus of Tuberculosis (x 1000) 





Bacillus of Typhoid Fever 



Bacillus of Typhoid Fever (x 1200) 

shov/ing flagellums 



& 

X 




Bacillus (Spirillum) of Asiatic Cholera Bacillus of Hog Cholera (x 1000) 

Fig. 63. Different Kinds of Bacilli. 

disease in every community. Our bodies furnish the very 
best soil for the germs. We do not need to go into the 
street to be exposed. These germs may be brought into 
the most cleanly houses upon one's clothing, or by the wind. 

How to avoid the Danger. — Of course, all such material 
known to be dangerous should be destroyed. If those 
suffering from such diseases were careful to burn all such 
matter, in time we might stamp out the diseases. But so 



1 1 8 Physiology. 

long as people spit upon the floors and pavements it will 
be difficult to prevent the spread of such germ diseases. 

In hospitals such matters are now looked after with the 
greatest care, and in private houses where there is intelli- 
gence on these subjects. Many of the railroad and street 
car companies now forbid spitting on the floors of cars 
and stations, not merely because it is uncleanly, but be- 
cause it is a means of spreading infectious diseases. 

Bacteria. — These disease germs are the smallest and 
simplest of living things. They are plants ; and while all 
of them that are well known have their scientific names, 
just as the larger plants have, they are all included in one 
general group called Bacteria. 

How to avoid Dust. — We need to learn a good deal 
more about avoiding and destroying dust, and the things 
that make it. Towns and cities need more sprinkling to 
keep the dust down. Much more of the refuse and street 
sweepings and cleanings ought to be burned. The dust of 
a house should always be burned, as we know not what 
germs of disease may be in it. If we burn it, we shall 
surely not have to sweep up that dust again. If we send 
it out of doors it may come back, and we may have to 
handle it again and again. 

Sweeping and Dusting. — So far as possible let us avoid 
things that make dust. When we sweep a carpet, a con- 
siderable share of the dust comes from the carpet itself, 
especially if the carpet is old. Curtains and tapestries of 
nearly all sorts not only hold dust, but contribute a good 
deal to it. Those who write on such subjects recommend 
hard wood floors with rugs instead of carpets. The rugs 
can be taken out of doors and shaken, and the floors wiped 
with a moist cloth, so that little dust is left floating in the 



Dust and Bacteria. 119 

air of the room. Compare this with the condition after the 
ordinary sweeping of a carpeted room with the common 
broom. The dust fills the air, only to settle back on the 
floor and furniture. Then comes the so-called dusting. 
But do we get rid of the dust ? For those who cannot have 
hard wood floors a most excellent substitute is oilcloth or 
linoleum. 

Sweeping the Sick Room. — The improved carpet 
sweepers are not only convenient, but sanitary. Many a 
well-meaning person will sweep a carpet in a sick room 
with an ordinary broom when the patient is suffering from 
lung disease, thoughtless of the fact that a little dust on 
the floor is of much less significance than dust in the air 
we breathe. No one likes dust on the' floor, but better a 
thousand times there than in our lungs. 

Lung Diseases. — Statistics seem to show that one 
seventh of the deaths among the civilized races is due to 
lung diseases. The best authorities are now agreed that 
consumption is not hereditary. But it appears that there 
may be inherited a tendency to this disease, so that, if ex- 
posed, such persons are more likely to contract the disease 
than others. Probably anything that lowers the general 
vitality makes the system more ready to yield to any of 
these contagious diseases. We have all noticed what a 
difference there is among individuals in the readiness with 
which they " catch" contagious diseases. 

How to ward off Contagious Diseases. — A good general 
condition of the body helps greatly to ward off diseases of 
this nature. A cheerful condition of mind and body should 
be cultivated. In times of widespread contagious disease, 
if one is terrified into the belief that he is going to have 
the disease, he is more likely to take it. Thorough clean- 



1 20 Physiology. 

liness, plenty of direct sunshine, care in diet, and the 
keeping of the body in good tone, reduce the chances of 
" taking" contagious diseases. An open-air life, abundant 
nutritious food, and freedom from anxiety are probably the 
best cures for the first stages of consumption. 

Destruction of Germs by Colorless Corpuscles. — The 

colorless blood corpuscles may take these germs of disease 
into their substance, and destroy or change them so that 
the disease is warded off. In other words, they may be 
compared to a cat that catches and eats the mice which 
invade a house. 

Germs killed by Plasma. — Sometimes the blood con- 
tains a substance that kills or prevents the action of dis- 
ease germs. Such a substance is called anti-toxin, which 
means a counteracting poison. But the blood of most 
persons does not naturally contain anti-toxin, and so, if the 
disease germs gain entrance, the disease follows. 

Danger of getting Germs into Wounds. — There is danger 
of introducing germs of disease in so simple an act as pick- 
ing out a sliver with a pin. If such germs happen to be 
on the point of the pin, the mischief is easily done. Great 
care should be taken in any such operation to use a 
thoroughly clean needle or lancet. Formerly any surgical 
operation that required opening the body cavity, either the 
chest or the abdomen, usually resulted in death. Now- 
adays such operations are commonly successful, because 
surgeons sterilize their instruments, hands, and everything 
used about the work. They kill any germs that might 
be introduced. In a word, they have learned to be 
clean. 

In caring for a patient ill of any germ disease, one should 
wash the hands in some disinfectant, such as chlorid of 



Dust and Bacteria. 121 

lime, and should not touch the fingers to the lips; igno- 
rance of these simple rules has caused many deaths. 

Malaria and Yellow Fever. — Malaria is due to an animal 
germ (not a bacterium) that gets into the blood. It is 
introduced by mosquitoes that have bitten persons whose 
blood contains these germs. The same is true of yellow 
fever. 

The Bacteria of Putrefaction. — Besides the disease- 
producing bacteria, there are others that cause decay and 
putrefaction of various kinds. They cause foods to " spoil," 
milk to turn sour, butter to become rancid, etc. 

While these bacteria do not cause disease in the human 
body, they often make food poisonous. The cases fre- 
quently reported of poisoning from eating ice cream, 
cheese, sausage, etc., are in many cases due to bacteria 
in them. We should, in the first place, be careful to get 
good, fresh material. In the second place, it should be so 
kept as to prevent the introduction and development of 
bacteria in it. Bacteria need heat and moisture for their 
growth just as higher plants do. 

The Preservation of Foods. — So our principal modes of 
keeping foods from spoiling are to keep them in a cold 
place, or to dry them. Or we heat them, and shut them 
away from the air, as in our various modes of canning and 
preserving foods. Salting and smoking meats, etc., pre- 
serve them by preventing the growth of bacteria. Cold 
does not usually kill bacteria. So milk that has been kept 
in a refrigerator, and that seems sweet, may have in it a 
stock of bacteria, and after we drink the milk the heat of 
our bodies favors their development. If milk is heated to 
i6o° or 170 F., any germs of tuberculosis present will be 

9 — PHY 



122 Physiology. 

killed. Boiled milk is less readily digested, and it is not 
necessary to boil it to kill most kinds of germs that it may 
contain. 

Summary. — i . Dust as mere dry, dead matter is irritating. 

2. Disease germs may form part of the dust of the air. 

3. Most of our contagious diseases are known to be due to bacteria. 

4. Burning is the surest method of destroying germs. 

5. Carpets, tapestries, and cloth-upholstered furniture add largely 
to the dust in houses. 

6. Putrefaction is caused by bacteria. 

7. Preservation of food depends on destroying, excluding, or retard- 
ing the growth of the bacteria of putrefaction. 

Questions. — 1. Is the air in the mountains or on the seashore better 
than elsewhere? 

2. What regions are recommended for consumptives ? Why? 

3. How is milk sterilized? 

4. Why do people seldom take cold while " camping out "? 

5. Why are the "steel grinders," in factories, short-lived? 

6. What occupations should be avoided by one who is predisposed 
to consumption ? 

7. What are some of the occupations suitable to those predisposed 
to consumption? 



CHAPTER XIII. 
EXCRETION. 

The Formation of Waste Matter in the Body. — All the 

force, or energy, of the body is produced by oxidation in 
the tissues; thought by oxidation in the brain; motion by 
oxidation in the muscles; and heat, wherever oxidation 
goes on. This oxidation produces waste matter in our 
bodies just as we have seen that oxidation in a stove 
produces waste matter. 

The Need of Removal of Waste. — When we waken on a 
cold winter morning we are likely to find that the fire in 
our hard coal stove has burned low. Not enough heat is 
given out. What is the trouble? Is it merely that more 
coal is needed ? We put another hod of coal in the maga- 
zine (though usually some remains). Does this bring the 
desired result? No. We open the draft. Is this suffi- 
cient? It is not. We must shake down the grate and 
clean out the clinkers. The removal of waste is as neces- 
sary as the addition of a fresh supply of fuel. In this case 
more necessary, for no amount of fuel will do any good so 
long as the ashes shut off the draft. In our bodies the 
removal of waste is still more important, because waste 
matter not only clogs the system, but, if present in any 
great amount, acts as a poison to the tissues. 

The Skin throws off Waste Matter. — The skin is 
constantly throwing off waste matter called sweat, or 
perspiration. 

123 



124 



Physiology. 



I, HAIR 



Epi- 
dermis 

Papilla . 



, 



Experiment to show Insensible Perspiration. — Thrust the hand into 
a cold glass jar. Note the moisture that soon gathers on the inside of 
the jar from the insensible sweat of the hand. A common fruit jar will 
do for a small hand, but a candy jar is better, having a larger mouth and 
clear glass. 

The Structure of the Skin. — The skin has two layers, 
the inner, or dermis, and the outer, or epidermis. The 

epidermis is thick 
over the palms and 
soles; elsewhere it 
is thin. The skin is 
much thicker than 
we would naturally 
suppose, and makes 
one fifteenth of the 
weight of the body. 

The Epidermis. — 

The epidermis con- 
sists of many layers 
of cells packed 
closely together. 
The deepest cells 
may be compared to 
grapes with their cell 
walls plumply filled out with the liquids of the cell. Sup- 
pose for the inner layer, grapes set on end, and so closely 
packed together as to press each other more or less flat on 
the sides. Above these are cells less closely pressed, more 
nearly spherical ; then cells with less liquid in them, and 
somewhat shrunken, like raisins. Then still dryer cells 
flattened parallel with the surface of the skin. And, last, 
in the outer part, layers of cell walls, dry and empty, pressed 
flat like empty grape skins. These flat cell walls come off 





W 


Dermis. 





Sweat 
Gland 


!i 


Blood 


'\\\ 



>A 



m 



Fat 
Cells 



Hair 
Bulb 



Tube 



Fig. 64. Vertical Section of the Skin. 



Excretion 



i*5 



in flakes (those from the scalp are called dandruff) from 
all the surface of the skin, and new cells are continually 
formed in the deeper layers. 



Mouth of Sweat Duct 



Horny Epider- 
mis 



Soft Laye. 




Papilla 



Dermis 



Artery 



Fig. 65- Section of Epidermis, showing Papilla. (Highly magnified.) 

The Color of the Skin. — The coloring matter, or pig- 
ment, of the skin lies in the deeper layer of the epidermis. 
In albinos the pigment is wanting. In persons with fair 
skin it is small in amount, in dark skins more abundant. 
Where the pigment is scattered irregularly it causes 
freckles, etc. 

A Blister. — A blister is caused by separating the outer, 
harder layer of the epidermis from the inner, softer, darker 
layer of the epidermis, as at B, in Fig. 64. Serum, or 
blood, fills the space between the separated layers. 



126 Physiology. 

The Dermis. — The dermis consists chiefly of tough, 
interlacing fibers. Hence the strength and durability of 
leather, which is the dermis preserved and prepared. The 
epidermis is usually removed in tanning. The dermis is 
richly supplied with blood capillaries and lymph capillaries, 
but the epidermis has neither. 

Papillas. — The outer surface of the dermis has many 
conical elevations, each of which is called a papilla. Over 
most of the skin they do not show on the outer surface, as 
the epidermis fills in the spaces between them, but is, itself, 
smooth on the outside. On the palms and soles the papillas 
are in rows, and these rows are indicated by the ridges. 

Hairs. — Hairs are outgrowths of the epidermis, but are 
deeply embedded in the dermis. They are supplied with 
blood at the tip of the root, where the growth takes place. 
The exposed part of the hair does not contain blood and is 
not sensitive. (See Fig. 64.) 

Hair-muscles. — There are small muscles connected with 
the roots of the hairs, by which the hair may be slightly 
moved. In the lower animals this power is much more 
used, as when the hair is made to stand erect on the back 
or tail of an angry cat or dog. The action of these muscles 
when frightened is what gives a peculiar feeling in the 
scalp, and to express strong fright we say, " It made his 
hair stand on end." 

Oil Glands. — The oil glands of the skin are distributed 
over all the surface except the palms and soles. The oily 
matter is usually poured out around the hairs as they 
emerge from the skin ; but some of the ducts open on the 
skin away from a hair. The oil serves to soften the skin 
and hair and keep them from becoming too dry. (See 
Fig. 64.) 



Excretion, 1 27 

Nails. — The nails, like the hair, are outgrowths of the 
epidermis. At the base the nail is supplied with blood, and 
here it grows. It is alive, hence this part is called the 
quick ; but at the outer surface and the tip it is dead. 

Examination of the Skin with a Lens. — Place a linen tester, or other 
hand magnifier, over the palm, and note the sweat pores or openings of 
the ducts of the sweat glands. Count the pores within the square shown. 
Measure this square, and then estimate the number of sweat glands to a 
square inch of the palm. 

The Sweat Glands. — The sweat glands are minute tubes 
whose inner ends are closed, and whose outer ends open 
upon the surface of the skin. The tube going inward pur- 
sues a corkscrew-like course through the epidermis, then 
becomes straighter, and is coiled up in a ball in the deeper 
layer of the dermis, or, more often, in the connective tissue 
just beneath the skin. (See Fig. 64.) The cells forming 
the walls of the coiled part are different from those of the 
duct, or straighter part of the tube. As the blood flows 
through the capillaries of the skin it gives off lymph. In 
this lymph are waste matters brought from the muscles 
and other tissues that have been at work. The sweat 
glands absorb this waste matter, with considerable water, 
and pass it out to the surface. 

Composition of Sweat. — Sweat is mostly water. About 
one per cent is solid matter, including salt and certain 
matter which like the organic waste matter from the lungs, 
easily putrefies. Sweat varies greatly in its wateriness and 
hence in the relative amount of solid matter contained. 
Ordinarily the sweat is evaporated as fast as it is poured 
out. In distinction from this insensible perspiration, there 
is the sensible perspiration — when it accumulates enough 
to be seen. These are not two kinds of sweat, but it is con- 
venient to distinguish between the visible and the invisible. 



128 Physiology. 

The Amount of Perspiration. — There is about one quart 
in twenty-four hours. It varies with (i) The temperature 
and dryness of the air. (2) The condition of the blood, 
e.g. if watery from drinking much water. (3) Muscular 
exercise. 

Gland Action and Blood Supply. — The sweat glands, like 
all glands, are largely dependent on the amount of blood 
supply. In exercising, the skin is usually redder from the 
greater supply of blood, and at the same time the glands 
are more active, for during exercise and for some time 
afterward there is more waste matter to be thrown out. 

Control of the Sweat Glands. — But the activity of the 
gland is not a mere filtering process ; it is not always in 
proportion to the amount of liquid present. There may 
be a cold sweat, i.e. when the skin is pale. This usually 
is due to excitement or emotion, which shows that the 
action of glands is under the control of the nervous system. 

Sweat Glands are Excretory. — The sweat glands rid the 
body of certain waste matters, and are therefore called 
excretory glands. A sweat gland is a simple gland. 

Distribution of Sweat Glands. — The sweat glands are 
thickly distributed over the whole surface of the body, but 
are especially numerous and large on the palms and soles. 
In the armpits the glands are also large. 

Regulation of the Temperature of the Body. — It is a very 
striking fact that, except in disease, the temperature of the 
body varies only a little from 98. 5 ° F. in winter and 
summer, during exercise and rest. The rate of producing 
heat varies greatly. The rate of giving off heat must 
therefore vary accordingly. 



Excretion. 1 29 

The Body gives off Heat. — In considering the regulation 
of the temperature of the body, we must bear in mind that 
the body is surrounded by air that is almost always con- 
siderably cooler than itself. The body is therefore almost 
always giving off heat. Our clothes do not warm us ; we 
warm them, and they keep us from warming the air too 
fast, i.e. they keep us from losing too much heat. Indoor 
air in winter should be kept at about 68° F. by artificial 
heat. This air does not warm us ; we, being about 30 F. 
warmer, are warming it. 

Ways of giving off Heat. — The skin gives off heat by — 

1. Radiation : heat is given off in every direction. 

2. Conduction: whatever we touch that is cooler than 
our bodies is warmed. We warm chairs, clothing, etc. 

3. Convection: the air in contact with the skin is 
warmed and rises. Our bodily heat is thus carried off by 
convection. 

4. Evaporation: the evaporation of sweat is the most 
important factor in regulating the heat of the body. Any 
liquid in evaporating absorbs heat. The cooling effect of 
alcohol, ether, or cologne on the skin is due to the fact 
that heat is taken from the skin in converting the liquid 
into a gas. 

Experiment in Evaporation. — With a medicine dropper put a drop 
of cologne on the back of the hand. Note two facts : (i) it produces a 
cooling effect ; (2) the liquid quicldy disappears. 

Practical Applications of this Principle. — We sponge a 
feverish patient to reduce his temperature. The cooling 
effect is due not so much to the coolness of the water itself 
as to the absorption of heat from the skin in evaporating 
the water. We sprinkle the floor in hot weather and thus 
cool the air of the room. 



130 Physiology. 

Heat and Exercise. — When we exercise we produce more 
heat ; we sweat more ; more heat is taken from the body 
to evaporate this sweat. If we are not exercising and are 
in cooler air, we sweat less, and less heat is given off. 
When we exercise there is more blood in the skin, and 
more heat is given off by radiation, convection, and con- 
duction. When we exercise less, the skin, especially in 
cool air, is paler, i.e. has less blood in it, and heat is econo- 
mized. Thus the temperature of the body is kept uniform. 

Distribution of Heat in the Body. — If more heat is pro- 
duced in one part of the body than in others, the circula- 
tion of the blood tends to equalize the temperatures of the 
different parts. So, too, if one part is cooled, i.e. is losing 
heat faster than others, the blood brings heat from other 
organs to that part. If the hands and feet are exposed to 
cold, it may do little good to have the rest of the body well 
covered. A pair of wristers and a pair of leggings may 
often add more to one's comfort than a heavy overcoat. 

Regulation of Temperature by Clothing. — In cold weather 
we put on more clothing and select non-conductors of 
heat, as woolen, leather, and fur. Many authorities recom- 
mend light woolen for summer wear, since with it we do 
not cool off so rapidly. 

Regulation of Temperature by Food. — In cold weather 
we eat more. We also eat more fat and other heat- 
producing foods. 

Effect of Wet Clothing. — In getting the clothing wet the 
cooling effect is not so much from the temperature of the 
water as from the loss of heat in evaporating the water 
from the clothing ; and this goes on for a long time. Of 
course it is desirable to put on dry clothing as soon as 



Excretion. 1 3 1 

possible. It is dangerous to sit down in wet clothing, even 
on a warm day. Children seldom take cold from wading, 
even in cold water, if barefooted ; but with wet shoes and 
stockings they are likely to take cold. 

Mechanical Protection by the Skin. — This is the most 
evident function of the skin. The skin is tough, strong, 
and elastic, hence well fitted to cover the body and yield 
with every motion, yet protect the softer and more delicate 
tissues beneath it from injury. 

Absorption by the Skin. — The skin has slight power of 
absorption ; hence there is some danger in handling cer- 
tain poisonous substances. The chief danger, however, is 
when there are cracks or sores on the hands. If one must 
handle suspicious material, it is well to rub the hands with 
vaseline. To use rubber gloves is safer still. 

Review of the Functions of the Skin. — (The skin as a 
sense organ will be considered later.) 1. Sensory. 2. 
Heat-regulating. 3. Absorptive. 4. Protective. 5. Ex- 
cretory. It will be easy to remember these five functions 
if it is noted that their initials spell the word s-h-a-p-e. 

Skin-grafting. — Sometimes after extensive burns, or 
other injury of the skin, bits of skin are taken from an- 
other part of the body, or from another person, and trans- 
planted to the injured part, where they grow. 

External Features of the Kidneys. — The kidneys are a 
pair of bean-shaped bodies attached to. the dorsal wall of 
the abdomen. (See Fig. 32.) The spot corresponding to 
the stem-scar of the bean is called the kilum. At this point 
are three tubes, the artery by which blood enters the kid- 
ney, the vein by which the blood leaves, and the ureter, by 
which the urine is conveyed to the bladder. 



132 Physiology. 

The Blood-supply of the Kidneys. — On entering the 
kidney the renal artery divides and subdivides, forming a 
very complicated set of capillaries. Through the thin walls 
of the capillaries certain waste matters pass into the cavity 
of the kidney, from which they are conveyed by the ureter 
to the bladder. (See Fig. 32.) 

Urea. — Urea is the nitrogen-containing waste of the 
body. There is nitrogen in muscle, brain, and in all the 
important organs of the body. When they work, some 
urea is formed. If the urea accumulates in the blood, it 
acts as a poison to the tissues. 

Importance of the Work of the Kidneys. — The kidneys 
are the only organs that can remove the urea from the 
blood ; hence their great importance. Small as they are, 
their removal would soon cause death. Urea is a solid, and 
could not very well be carried out of the body unless dis- 
solved. So the urine consists mainly of water containing 
urea, salt, and various other substances in small amounts. 

Relation between the Kidneys and the Skin. — There is a 
very close relation between the kidneys and the skin. In 
warm weather, and when exercising actively, we sweat more 
and the kidneys excrete less water ; on the other hand, 
when we exercise less, and especially in a cool place, we 
sweat less, and the amount excreted by the kidneys is in- 
creased. For instance, when one has a cold he is 
more or less feverish ; that is, the action of the skin is inter- 
fered with, and there is less perspiration. At such time 
the kidneys have more work to do, and may be so over- 
worked as to injure them permanently. 

Summary. — 1. When the body works it produces waste matter. 

2. Waste matter must be removed or it will poison the body. 

3. The skin throws off sweat, — mostly water carrying waste matter. 



Excretion. 133 

4. Sweat is taken from the lymph by the sweat glands, which are 
coiled tubes, opening on the surface of the skin. 

5. The skin consists of two layers, the dermis and the epidermis. 

6. The amount of sweat varies with heat, exercise, food, etc. 

7. The body gives off heat by (i) radiation, (2) conduction, (3) con- 
vection, (4) evaporation. 

8. The temperature of the body in health stays at about 98. 5 F. 

9. The temperature is regulated by the evaporation of sweat. 

10. Heat is distributed through the body by the blood. 

11. In cold weather we eat more fat, and other food, to make heat. 

12. The skin has five functions: touch, heat-regulation, absorption, 
protection, excretion. 

13. The kidneys remove urea from the blood. Urea is the nitrogen- 
containing waste of the body. 

14. If much urea is in the blood, the body is poisoned, and the re- 
moval of the kidneys would soon cause death. 

Questions. — 1. Do dogs, cats, and cows sweat? 

2. Why is thirst relieved by moistening the skin? 

3. Why is it a good sign when the skin of a feverish person becomes 
moist ? 

4. Why should clothing worn during the day be removed at night? 

5. Can food, medicine, or poison be absorbed through the skin? 



CHAPTER XIV. 

FOODS AND COOKING. 

Necessity of Food. — Thus far we have been studying 
processes by which* the body's weight is reduced. We 
have studied the oxidation in the tissues and the removal 
of the wastes. Unless the tissues receive a supply of new 
material, the heat and energy of the body cannot long be 
kept up. 

Food Defined. — Foods are substances that build tissues 
or produce energy without injuring any organ or function 
of the body. Certain substances that do not become part 
of any tissues, nor in themselves produce energy, are use- 
ful in aiding the processes going on in the body, These 
may be called accessory foods, e.g. condiments, such as 
pepper. 

Foods and Foodstuffs. — Most of our articles of food 
consist of two or more different kinds of materials. For 
instance, milk consists (i) chiefly of water; and in it are 
(2) the substance that makes cheese (casein); (3) cream, 
from which we get butter (fat); (4) sugar, which gives 
milk a sweet taste; (5) salts, such as common salt, lime 
salts, etc. These different materials are foodstuffs. We 
have many kinds of foods, but few foodstuffs, which we 
find occurring over and over again, in various forms, in 
the numerous things we eat. 

i34 



Foods and Cooking. 135 

Kinds of Foodstuffs. — 1. Proteids (example, casein). 

2. Fats. 4. Water. 

3. Carbohydrates (starch and sugar). 5. Salts. 

The Proteids. — The chief substance in the white of an 
egg is albumen, a typical proteid. Of the many proteids 
some of the more commonly known are casein (the curd 
of milk), gluten (in grains), legumin (in peas and beans), 
fibrin (in blood), myosin (in muscles). Gelatin (obtained 
from connective tissue and bones by prolonged boiling) 
differs considerably from the proteids in composition, but 
may be counted in with them. It is less valuable as a food 
than the true proteids, although in certain circumstances 
more desirable from the fact that it is very easily digested. 

Importance of Proteids. — The proteids are of special 
importance as foods because the most active tissues — 
those of the muscles, nerves, and glands — and the most 
important liquids of the body, e.g. blood and lymph, con- 
tain proteid. Proteid food, therefore, must be taken to 
make good the losses of these tissues during their oxida- 
tions. Proteid is the only foodstuff containing nitrogen. 

Proteid-containing Foods. — The principal proteid-contain- 
ing foods are lean meat, fish, eggs, milk, cheese, and some 
seeds which abound in the vegetable proteids. 

Meat. — Lean meat has about twenty per cent of proteid, 
the rest being chiefly water. Beef and mutton are more 
easily digested than veal and pork. Pork sometimes con- 
tains a parasitic worm called trichina, which causes illness, 
or even death, if eaten. Pork should be thoroughly cooked 
so as to kill the trichinas. 

Fish. — Fish, when fresh, is a good food. Although, as 
a rule, salted meats are less easily digested than fresh, 



136 Physiology. 

salted codfish is a nourishing and economical food. Fish 
is not an especially valuable brain food, as commonly 
believed. 

Eggs. — Eggs contain considerable proteid, but their value 
as food has been overrated. The yolk has a large amount 
of fat. Although the egg has all the material needed to 
form a chick, it is not a perfect food for man. 

Milk. — Milk, as we have seen, is an ideal food, in that 
it contains all the kinds of foodstuffs, and in the right pro- 
portion for the young mammal. But the proportions are 
not right for the adult. An adult would need four quarts 
and a half daily, and then he would not get enough carbo- 
hydrates (represented in milk by the sugar). The oily 
material in milk is in the form of minute globules, which 
can easily be seen under the microscope. Each of these 
oil droplets is surrounded by a thin envelope of albumen, 
by means of which it is enabled to remain suspended for 
some time instead of rising quickly to the surface. Such a 
mixture of oil in a liquid is called an emulsion. When 
cream is churned the albuminous covering is removed and 
the butter " gathers." 

Cheese. — Cheese is very rich in prcteid, much more so 
than lean meat. Yet, as it is hard to digest, we do not use 
it much as food; we regard it more as a luxury, while in 
many parts of Europe it is largely used as food, taking the 
place of meat. It is a cheap food, and might well be used 
more extensively, especially by laboring men. When taken 
with milk, it is said to be more readily digested. 

Vegetable Proteids. — Peas and beans (dried) contain as 
much proteid (legumin) as meat, and all the cereals contain 
some proteid (gluten). 



Foods and Cooking. 137 

Fats. — Fats are composed of carbon, hydrogen, and 
oxygen. The oxygen is small in amount, so these foods 
yield a great amount of energy by the oxidation of their 
carbon (forming carbon dioxid) and hydrogen (forming 
water). The fats most used are animal fats, including 
butter. But some vegetable oils, such as olive and cotton- 
seed oils, are used. 

The Carbohydrates. — Starch and sugar are the chief 
carbohydrates. They are composed of carbon, hydrogen, 
and oxygen, but not in the same proportions as in fats. 
Starch is used in larger quantity than any other foodstuff 
except water. Sugar is usually regarded as a luxury, yet 
it is an important food. It is quickly absorbed. 

Carbohydrate-containing Foods. — The principal carbo- 
hydrate-containing foods are the grains, vegetables, and 
fruits. The most important grains are wheat, corn, rice, 
oats, rye, and barley. 

Wheat — Wheat furnishes the principal breadstuff among 
the more civilized nations. It is especially adapted to the 
temperate zones. Taking into consideration its composi- 
tion, digestibility, and other characteristics, it is the most 
desirable of all the grains. 

Wheat Flour. — In ordinary white flour nearly all the 

gluten has been removed with the bran or "middlings." 

While wheat or bread made from the whole grain of the 

wheat may support life, one would starve if he tried to live 

on common white bread alone. It is almost entirely starch. 

In the ''entire wheat flour" it is claimed that all the gluten 

is retained, only the very thin outer husk of the grain being 

removed. It does not make so white a flour, but it is better 

adapted to use as a food. If we use white bread, having 

thrown away the nitrogenous part of the wheat, we need to 
10— PHY 



138 Physiology. 

take more proteid from other sources than if we used the 
entire wheat flour. This is not economy. It is claimed 
that the entire wheat bread is more wholesome as well as 
more nutritious. The part thrown away has in it phos- 
phates as well as the nitrogenous material. This flour is 
ground fine so that it has not the coarse particles which are 
in Graham flour, and which are, in some persons, a source 
of irritation to the mucous coat of the digestive tube. 

Corn. — Corn is one of the most nutritious of the grains. 
Although somewhat less readily digested than similar 
preparations of wheat, and, consequently, less desirable 
for indoor workers, it is a fact that, for a given amount of 
money, more nutriment can be obtained in corn meal than 
in any other food known. 

Rice. — Rice forms a larger part of human food than the 
product of any other plant, being often an almost exclusive 
diet in India, China, and the Malayan islands. Rice has a 
larger proportion of starch, and less of fats and proteids, 
than the other grains. It is best adapted for the food of 
warm climates. 

Oats. — This grain was first used as food for man by the 
Scotch, but the use has extended and become prevalent in 
this country. In point of nutrition it is ranked higher by 
some than ordinary grades of wheat flour. 

Rye. — Rye grows farther north than other grains, and 
is largely used for bread in Russia and parts of Germany. 
It is a valuable food, though less nutritious and less digest- 
ible than the corresponding preparations of wheat. 

Barley. — This grain has wide range of cultivation, and, 
while inferior to wheat, is considerably used where other 
grains cannot be raised. 



Foods and Cooking. 139 

Potatoes. — Potatoes contain about twenty per cent starch, 
two per cent of proteid, and no fat, the remainder being 
chiefly water, with some useful salts, especially potash salts. 
In spite of its relatively low food value, the potato is our 
most useful vegetable on account of its abundance, the ease 
with which it can be preserved, and the readiness and the 
variety ,of ways in which it can be cooked. 

Other Vegetables. — The chief nutrient in vegetables is 
starch, though in many the starch is present in small amounts. 
The salts and acids present are of value, and care should 
be observed not to remove too much of these salts in cook- 
ing. The fibrous matter, cellulose, while indigestible, is of 
value in adding bulk to the mass of food to be digested. 

Scurvy. — Formerly sailors were subject to scurvy; this 
is now attributed to a diet of fat and salt meat, to the 
exclusion of fresh vegetables, etc. The disease is avoided 
by a greater use of vegetables, lime juice, etc. 

Fruits. — Many of the fruits, such as bananas and 
apples, have considerable starch and sugar. But the 
fruits are more useful to us on account of their flavor, 
due to aromatic bodies, and to their salts and the peculiar 
fruit acids. 

Water. — Water constitutes about two thirds of the 
entire weight of the body. It constitutes the bulk of the 
liquids we have studied, blood, lymph, sweat, saliva, bile, 
etc. Water dissolves and carries all the material of the 
body. Hence we need a large amount of it ; of course we 
must remember that we get a good deal of water in most 
of our solid foods. 

Rain Water. — Water, as it comes from the clouds, is 
pure. After enough rain has fallen to wash the air, rain 



1 40 Physiology. 

water is pure, and if caught on a clean roof (especially a 
slate roof) and kept in a clean cistern, it is good drinking- 
water. 

Well Water. — Falling upon the earth, the rain water 
filters down until stopped by some layer, such as clay, 
through which it cannot soak. This water is the supply 
of our wells and springs. It always has more -or less 
earthy matter, especially lime, in solution, and is therefore 
more or less " hard." Unless a large amount of mineral 
matter or some special material is dissolved in it, it is 
ordinarily good drinking-water. Such water is not pure, 
in the strict sense of the word, but is pure for drinking 
purposes. 

Impurities in Water. — The great source of danger is 
from what are called ''organic" impurities. Bacteria do 
not thrive in pure water. They must have something on 
which to feed and grow. But in water containing a large 
amount of decaying animal or vegetable matter they are 
likely to abound. And the most dangerous sources of 
contamination are cesspools and sewers. Water may be 
contaminated by such material and not have bacteria in 
it, but is very likely to harbor such foes. 

Contamination from Cesspools. — The ordinary cesspool 
is a grave source of danger. Because the well may be on 
higher ground than the cesspool does not give assurance 
that the water may not be polluted. Often when the sur- 
face of the ground slopes in one direction, the strata 
underneath may slope in the opposite direction, and the 
well may be the reservoir into which the cesspool is 
drained. Good authorities say that a cesspool should not 
be allowed within a hundred feet of a well. 



Foods and Cooking. 141 

Abolish the Cesspool. — It is better and safer to have 
no cesspool. Where a sewer system is not to be had, it is 
better to allow no great accumulation of such material. A 
deep pit in which a quantity of semiliquid matter gathers 
is not only a nuisance but a source of danger. Privies 
should have a very shallow pit, or none, and should be 
cleaned often. There should be a little dust sprinkled in 
each day, and occasionally some chlorid of lime or sulphate 
of iron. 

Typhoid Fever. — Typhoid fever is usually caused by 
drinking-water. The excretions of some one who has had 
the disease find their way into the source of the drinking- 
water. In many cases this has been clearly proved. Of 
course the excretions of all such patients should be either 
destroyed or thoroughly disinfected. 

Ice Water. — Although bacteria will not develop in a 
cold place, they are not killed when frozen in ice, as 
was formerly supposed. Further, ice, in forming, does 
not throw out all the impurities, as was formerly believed. 
So it is not safe to drink water formed from melted ice 
unless the water of which that ice was made was good 
water. The ice taken from ponds is not safe. If ice is 
made artificially from suitable drinking-water, the melted 
product will be essentially unchanged so far as the com- 
position is concerned. Water may be cooled by placing 
any ice around it, and we may have the desired tempera- 
ture without danger. 

Boiling Water. — When one cannot get good drinking- 
water, or when away from home where the water is of 
doubtful purity, it is better to boil the water before using 
it, either as a drink or in preparations of food that are not 
to be thoroughly cooked. It seems to be proved that it is 



142 Physiology. 

better to heat the water twice nearly to the boiling point 
than to boil once only. The first heating may start the 
germs into more active life, causing them to sprout (so to 
speak), and a second heating several hours later may easily 
kill them ; whereas it has been proved that one hard 
boiling will not always kill the germs. 

Cautions as to Drinking-water. — If one uses tea and 
coffee, it is safer to content one's self with these, and not 
drink much water till that which is safe, as from deep 
wells, can be obtained. In hot weather, and especially 
for those who are engaged in hard work, it has been 
found that a little oatmeal stirred in the water is bene- 
ficial. When overheated, avoid drinking much cold water. 
Repeatedly rinse the mouth with cool water, and swallow 
very little. This is the way trainers manage a horse at a 
race, and it is sensible to treat a man as carefully. 

Salts. — Salts include many substances besides common 
salt. They aid in the solution of various substances dur- 
ing digestion and in other processes. We cannot live 
without them. Lime in the form of calcium phosphate and 
calcium carbonate is essential, especially in the bones and 
teeth. 

Necessity of a Mixed Diet. — Our experience, together 
with the results of experiments on animals, teaches that 
we could not live long if fed on any one class of food- 
stuffs alone. We must take a representative of each of 
the groups. We have noticed that most of our foods 
already contain more than one foodstuff. We so combine 
them as to get suitable proportions. Thus we eat bread 
and butter (a small amount of fat with a large quantity of 
starch and a little gluten), meat and potato, crackers and 
cheese, pork and beans, egg on toast, bread and milk, rice 



Foods and Cooking. 143 

and fowl, macaroni and cheese ; they " go well together " 
chiefly because each contains what the other lacks. 

Disadvantages of a One-sided Diet. — In order to get 
enough nitrogen from bread alone, one would have to eat 
about four pounds a day ; meanwhile twice as much car- 
bon as is needed would be taken, thus throwing an undue 
amount of work upon the digestive organs. Again, one 
would need to consume about six pounds of meat to get 
the requisite amount of carbon, and six times as much 
nitrogen as is needed would be taken ; to get rid of this 
extra nitrogen would severely tax the kidneys and liver. 

Effect of Cold on Appetite for Fats. — In cold climates 
a large amount of fat is consumed, while in the tropics 
starch is the chief food. Our appetites call for more of 
the fatty foods during the winter season. 

Proper Diet. — While common experience has led people 
to adopt a mixed diet, the proportions of the different food- 
stuffs is not always what it should be. The proportions 
of the foodstuffs (exclusive of water) may be roughly stated 
as about 1 part of proteid, 1 part of fat, 3 parts of carbo- 
hydrates. But this will vary somewhat with the amount 
of work done, and other varying conditions. 

Vegetarians. — The so-called " vegetarians " recognize 
the need of proteid food, and most of them seek proteid in 
eggs, milk, and cheese. But these are animal products, 
and the name " vegetarian " is inconsistent. They are 
merely " anti-meat eaters." That we are adapted for 
using flesh as part of our food is indicated in at least two 
anatomical features : (1) we have canine teeth, though not 
so fully developed as in the carnivora ; (2) the intestine in 
carnivora is very short, that of the herbivora very long, 



144 Physiology. 

but in man intermediate. Nevertheless, it is undoubtedly- 
true that many persons eat too much meat. 

Beef Tea. — Beef tea and various beef extracts are help- 
ful. There is not enough nourishment in them to maintain 
strength without other food. But many of the soups and 
drinks made from them are beneficial. They refresh the 
tired system wonderfully. If the man who feels " fagged 
out" and takes a drink of liquor to " brace him up," as he 
says, were to take a cup of hot bouillon, he would find him- 
self " braced up," for the time, without any bad reaction, 
or permanent injury to the system. 

Cooking. — Cooking is designed to make food more pala- 
table and more digestible. Some foods, such as eggs, are 
as digestible before they are cooked as after. But many 
foods in the raw state are unattractive, whereas cooking 
usually develops an agreeable odor and -taste. Cooking 
should soften the harder and tougher tissues, such as cellu- 
lose in vegetables and the connective tissue of animal foods. 
Cooking starch causes the starch grains to swell and burst, 
and makes the starch more digestible. 

Making Soup. — If meat be cut into small pieces and put 
into cold water, and the water gradually warmed, the solu- 
ble material of the meat may be extracted, and this is the 
principle followed in making soups. 

Boiling Meat. — If we wish to cook the meat itself, the 
juices should be retained instead of withdrawn. For this 
purpose boiling water is poured over the meat to coagulate 
the outer layer and prevent the extraction of the juices. 

Baking, Roasting, and Broiling. — The same principle 
applies to baking, roasting, and broiling. The outside is 
subjected to high heat at the beginning of the cooking, 
which forms a sort of crust through which the nutritious 



Foods and Cooking. 145 

juices cannot escape. In these modes of cooking it is very 
desirable to reduce the heat after the first few minutes, so 
that the interior may be cooked enough without over-cook- 
ing the outside ; this is especially true in broiling. 

Frying. — Frying, as ordinarily done, is not a good mode 
of cooking ; in fact, is often very bad, as the food is fre- 
quently soaked with fat and rendered indigestible. But 
true frying, that is, by immersion in boiling fat, is a good 
mode of cooking. This coagulates the albuminous sub- 
stance on the outside, keeps in the nutritious juices, and 
prevents soaking with the fat. 

Summary. — i . Food is to build tissue or produce energy. 

2. Foodstuffs are the simpler materials in foods. 

3. The foodstuffs are proteids, fats, carbohydrates, water, salts. 

4. The proteids are albumen, casein, gluten, legumin, fibrin, myosin, 
gelatin. 

5 . They are found in meat, egg, milk, peas, beans, and a little in grains. 

6. The carbohydrates include starch and sugar. 

7. Starch is obtained from potatoes and the grains. 

8. The most important grains are wheat, oats, corn, rice, and rye. 

9. Wheat is considered the best grain, though more nourishment 
can be obtained from corn meal, for a given amount of money, than from 
any other food. 

10. Vegetables contain some starch, but are of value from giving 
bulk to the food. 

1 1 . Water containing decaying organic matter is dangerous to drink, 
because it is likely to contain bacteria, which poison us or cause disease. 

12. Boiling water usually kills the bacteria in it. 

13. Drinking ice water is injurious. 

14. We take a mixed diet, as no one food contains all we need. 

15. Cooking is to render food more palatable and digestible. 

Questions. — i. Is the appetite always a safe guide in eating? 

2. Which kind of foodstuff is most expensive? Why? 

3. Why is bread the " staff of life " ? 

4. Make a list of the common foods, naming the foodstuffs in them. 

5. How do flour and potatoes compare in cheapness? 



CHAPTER XV. 
THE DIGESTIVE SYSTEM. 

DIGESTION IN THE MOUTH. 

The Object of Food. — The tissues are worn out by their 
oxidation. They are built up again by the blood, and the 
blood is renewed by the food. 

The Digestive Tube. — All food must be reduced to the 
liquid condition, if it is not already liquid. The chief organ 
in this work of liquefying the food is the digestive tube, or 
" alimentary canal." As the food passes through the 
digestive tube it is ground and liquids are poured upon it. 
Thus it is reduced to a liquid that can be absorbed and 
taken into the blood. 

The Work of the Digestive Tube. — To take a special 
instance, a muscle is in part worn out by the oxidation 
during its activity ; to replace the loss suppose we take a 
piece of steak. We cannot substitute this directly in the 
place of the worn-out tissue. In digesting the steak we 
must tear it to pieces, and reduce it to a liquid form by the 
action of the teeth and by the various liquids from the 
glands along the digestive tube. The beefsteak, as such, 
must be thoroughly destroyed ; in the liquid produced by 
the digestion of the beef there is no trace whatever of the 
structure of the beef. But the blood, taking this material, 
builds muscle which can hardly be distinguished from the 
original beef. 

146 



The Digestive System. 147 

If the food taken is a liquid and ready to build tissue, as 
a thin syrup, it will not need to go through these changes. 

The Organs of Digestion. — The organs of digestion are 
the digestive tube, with the masticating organs, and the 
glands in and along the walls of the tube. 

The parts of the digestive tube are the mouth, the 
pharynx, the gullet (or esophagus), the stomach, the small 
intestine, and the large intestine. 

The Mouth and Gullet. — At the back of the mouth may 
be seen the soft palate with the cylindrical uvula hanging 
from its center. Beyond this is the cavity of the pharynx, 
which narrows below into the gullet, a red-walled, muscular 
tube, extending along the back side of the windpipe, and 
close to the spinal column. It extends the length of the 
chest, and then passes through the diaphragm and widens 
into the stomach, at the upper left end of the latter. 

The Stomach. — The stomach is somewhat pear-shaped, 
with the larger end to the left. At the right end it tapers 
into the small intestine, the first foot or so of which is 
called the duodenum. (See Figs. 53, 72, and 74.) 

The Liver and Pancreas. — Just below the diaphragm is 
the dark-colored liver, overlapping a large portion of the 
stomach. Between two of the three lobes of the liver is the 
bile sac, whose duct enters the duodenum a short distance 
from the stomach. The pancreas is a pinkish organ of 
irregular shape lying along the stomach and duodenum. 
Its duct enters the duodenum at the same point as the bile 
duct. 

The Intestine. — The first part of the intestine is the 
small intestine. At the lower right part of the abdomen 



148 



Physiology. 




this enters the larger intestine. The intestine is held 
in place by the mesentery, a thin fold of transparent 

membrane folded closely 
around it, and supported 
from the back wall of 
the abdominal cavity. 
Between the two layers 
of the mesentery are the 
branches of the artery 
supplying the walls of 
the intestines, and the 
veins that convey the ab- 
sorbed food from the 
intestine to the liver. 

Figf. 66. Cross-section of Abdomen. _„ __ ,« ~ t 

* The Mouth. — The 

pupil should carefully examine his own mouth by means 
of a mirror. We are apt to think of the mouth as a cavity 
of considerable size, as indeed it is when fully opened; 
but we are not so likely to think how completely the cavity 
disappears when the mouth is closed. If one notes the 
sensations from the mouth when it is closed, he will per- 
ceive that the tongue almost entirely fills the space, touch- 
ing the roof of the mouth, and the teeth in front and at 
the sides. 

The Tongue. — The tongue consists chiefly of muscles, 
running in different directions, thus giving it a variety of 
motions. The tongue is the chief organ of taste, and is 
therefore (with the sense of smell) the gate-keeper of the 
digestive tube. The tongue has also a keen sense of 
touch, and so is useful in detecting and removing any 
food particles that may remain on the teeth after eating, 
During mastication the tongue, with the lips and cheeks, 



The Digestive System. 



149 



keep the food between the teeth. When the morsel of 
food is sufficiently masticated, the tongue pushes it back 
into the pharynx to be swallowed. 

The Teeth. — The teacher can usually obtain a supply of teeth from 
the dentist for the asking. These should be cleaned before using them 
in the class. Use pearline or any washing soda. Let each pupil make 
a drawing of one of each of the four kinds of teeth ; draw both a front 
(outer surface) and a side view (surface adjacent to another tooth) of 
all but a molar. 



Longitudinal Section 



Side View 



Face View 



. Enamel 

[|_ Pulp Cavity 
Dentine 
Cement 




Crown 



Root 



! Hole for Blood Tubes and Nerves. 

Fig. 67. Parts of a Tooth. (Incisor.) 




External Features of a Tooth. — Examine one of the 
front teeth. It has the following parts : — 

1. The crown, the part that is above the gum. 

2. The root, the part that was buried beneath the gum. 

3. The neck, dividing the crown from the root 

4. A hole at the tip of the root. 

To make a Section of a Tooth. — Let each pupil prepare a longitudi- 
nal section of a tooth as follows : Embed a tooth in a little sealing wax 
on the end of a spool, cork, or block of wood. With a grindstone grind 
away one half, showing the pulp cavity to the tip of the root, as in 
Fig. 67. Make a drawing of the surface thus exposed, naming the 



150 Physiology. 

parts. If human teeth cannot be obtained, almost any kind will serve. 
Let each pupil keep his preparation. 

Structure of a Tooth. — 1. The pulp cavity, communi- 
cating with a hole in the tip of the root, through which 
the nerve and blood tube entered. 

2. The bulk of the tooth is made of a substance called 
dentine (ivory). 

3. The crown of the tooth has a covering of enamel, a 
very hard substance. 

4. The root is covered with a bony substance, called 
cement. 

The Arrangement of the Teeth. — Beginning at the middle 
of the front of the mouth, there are (in the normal adult) 
eight teeth in each half jaw : two incisors, one canine, two 
bicuspids (or premolars), and three molars (see Fig. 68). 

Dental Formula. — The kinds and arrangement of teeth 
are expressed by a dental formula, in which the nume- 
rators indicate the upper jaw and the denominators the 
lower, thus : If, C^, PMf , Mf (for one side of the head). 

The Kinds of Teeth. — The crown of an incisor is chisel 
shaped ; but the root is flattened in the opposite direction, 
i.e. at right angles to the jaw, instead of parallel to it, as 
in the crown. The canine tooth has a conical crown, and 
a longer root than the incisor. The bicuspid has two 
points. The molar has a cube-shaped crown, and usually 
two or three roots. 

The Milk Teeth. — The thirty-two teeth of the perma- 
nent set were preceded by a temporary set of twenty milk 
teeth. Because the first set is temporary, it should not 
therefore be neglected. Cavities in these should be filled 
and the teeth kept clean. Before the temporary set has 



The Digestive System. 



T 5* 



gone the first of the permanent set appear. The first of 
these, often called the " six-year molars," are just back of 
the hindermost "milk molars." These should receive 
especial care, as they will never be replaced. Any begin- 
ning of decay in them ought to receive prompt attention. 



KINDS OF TEETH 
Incisors 



Canine 



Upper 



Molars 




TIME OF APPEARANCE 
7th Month 
9th " 
18th •« 

12th " 

24th M 



TEMPORARY SET 

Upper 



Bicuspids 




Lower 
PERMANENT SET 

Fig. 68. TEETH : Kinds, Arrangement, and Times of Appearance. 

The Care of the Teeth. — The teeth need careful atten- 
tion. They should be thoroughly brushed at least twice a 
day, on rising and on going to bed. It would be better to 
clean them after each meal also. If a tooth powder, recom- 



152 Physiology. 

mended by a reliable dentist, is not used, a good white 
castile soap will serve well. It is better to use tepid water. 
Toothpicks are useful in removing the larger particles. 
Quill toothpicks are best; metal should never be used. 
The teeth should be examined twice a year by a dentist, 
and any cavities promptly filled. 

Cause of Decay of Teeth. — If the teeth are not thoroughly 
cleaned the particles of food which remain will soon begin 
to decay. This decay is caused by the growth of germs, 
usually some kind of bacteria, and the decay thus begun 
is likely to develop acids which attack the limy material 
of which the teeth are composed. When it is necessary 
to take acid medicines, care should be taken not to let 
them come in contact with the teeth. Sweet substances 
are very likely to decompose and form acids ; so we must 
clean the teeth after eating candies. When the teeth are 
neglected, a limy substance, called tartar, forms on them 
and encourages decay. 

The Salivary Glands. — The salivary glands make the 
saliva and pour it into the mouth. There are three pairs 
of salivary glands — the parotid, just back of the angle of 
the jaw, under the ear ; its duct opens on the inside of the 
cheek opposite the second molar of the upper jaw. The 
submaxillary gland lies under the angle of the jaw ; its 
duct opens under the tongue near the front of the mouth. 
The sublingual gland is in front of the submaxillary and 
empties under the tongue (see Fig. 74). 

Salivary Ducts in our Mouths. — If the inside of one's cheek be 
examined by the use of a hand mirror, the opening of the duct from the 
parotid gland may be seen opposite the second molar of the upper jaw. 
It usually looks like a pink and white spot, resembling a wound of a 
bee sting. Sometimes saliva may be seen issuing from it. 



The Digestive System. 153 

Action of the Salivary Glands. — The salivary glands 
pour into the mouth a liquid which they make from 
materials taken from the blood. In structure the gland 
may be compared to a bunch of grapes, the grapes repre- 
senting the little cavities, with a wall of cells that make 
the saliva. From each of these cavities the liquid passes 
into its duct, represented by the stem of a single grape; 
many of these unite to form the main duct, which corre- 
sponds to the main stem. A thick network of capillaries 

Mucous Membrane 



-Duct of Gland 



— Secreting Cells 



Vaso- dilator — 
Nerve 



Fig. 69. Diagram of a Salivary Gland. (After Landois and Stirling.) 

surrounds the gland ; the liquid part of the blood (plasma) 
soaks out through the capillary walls and surrounds the 
gland ; it is now called lymph ; from the lymph the gland 
directly obtains its material. 

Nerve Control of Salivary Glands. — The glands are 
doubly dependent on nerve control : — 

1. Through the nerve control of the muscles in the 
walls of the arteries the amount of blood sent to the 
glands is regulated. 

2. Nerves also go to the cells of the gland to control 
their activity. When we taste, smell, see, or even when 
we think of, some delicious food the mouth may "water," 



t 54 Physiology. 

as we say, i.e. the salivary glands are, by reflex action, 
stimulated to activity ; on the other hand, some emotions, 
such as fear, check the flow of saliva. 

Saliva and its Uses. — The saliva is mostly water, and, 
when we are not eating, serves (i) to keep the mouth moist. 
The water of the saliva soaks the food during mastica- 
tion and (2) helps the process of grinding; it (3) enables 
us to taste by dissolving any food that is soluble ; it 
further (4) enables us to swallow what would otherwise 
be a dry powder. The special element of the saliva, 
ptyaliriy has the power (5) of changing starch to sugar. 

Amount of Saliva. — The amount of saliva secreted 
daily is estimated at three pints. Of course the glands 
should be allowed to rest between meals. The habit of 
chewing gum, though supposed to aid digestion, undoubt- 
edly does far more harm than good. During the resting 
period the glands accumulate material for the active work 
of secretion, for there is no sac in which to store the 
saliva, and it must be made as fast as is needed. 

Mucous Glands and Mucus. — Besides the salivary glands, 
there are great numbers of simple glands in the mucous 
membrane lining the mouth. These secrete a clear sub- 
stance called mucus, resembling white-of-egg. It is mucus 
in saliva that makes it "stringy." 

Mumps. — In the mumps the salivary glands are in- 
flamed and painful. This is most noticeable in the 
parotid gland, which feels the pressure of the lower jaw 
in the attempt to chew. 

Summary. — 1. The chief work of digestion is to make the food into 
a liquid, ready to be absorbed and become part of the blood. 

2. The digestive system consists of a long tube, through which the 
food passes, being subjected to mechanical and chemical processes. 



The Digestive System. 155 

3. The parts of the digestive tube are the mouth, gullet, stomach, 
and intestines. 

4. Along this tube are several large glands, such as the salivary 
glands, pancreas, and liver, which make liquids to pour upon the food. 

5. The tongue is composed of muscles, is very movable, and 
( 1 ) tastes the food ; (2) keeps the food between the teeth during 
chewing; (3) aids in swallowing. 

6. A tooth has crown, neck, and root. 

7. The tooth consists of dentine, containing a pulp cavity. The 
crown is covered with enamel, and the root is covered with cement. 

8. There are thirty-two teeth in a full set, eight in each half jaw, 
beginning at the front, two incisors, one canine, two bicuspids, and 
three molars. The first set of twenty teeth are called " milk teeth." 

9. The teeth must be kept clean by brush and tooth powder. 

10. There are three pairs of salivary glands, parotid, submaxillary, 
and sublingual. Their action is controlled by nerves.. 

1 1 . The chief use of saliva is to change starch to sugar. 

Questions. — 1. Why should we not crack nuts with the teeth ? 

2. Why does the physician examine the tongue of his patient? 

3. Is it well to eat much soaked food? Why not? 

4. How many teeth have you, and of what kinds? 

5. Why is gum-chewing injurious? 



CHAPTER XVI. 

DIGESTION IN THE STOMACH. 

The Pharynx. — The cavity back of the mouth, beyond 
the soft palate, is the pharynx. The pharynx is a funnel- 
shaped cavity, connecting above with the passages from 
the nostrils; in front it opens into the mouth; below it 



Hard Palate""' 




Eustachian Tube 



Soft Palate, Down 



L — Pharynx 

Epiglottis, Raised 

Gullet, Closed 
Glottis, Open 



Fig. 70. Positions of the Organs of the Mouth and Throat during Breathing. 

connects with the windpipe, through the glottis, and with 
the gullet, which lies just back of the windpipe (see Figs. 
70 and 71). 

Position of Organs during Respiration. — In quiet respira- 
tion the tongue nearly fills the mouth. The base of the 
tongue is nearly covered by the soft palate, which curves 
downward from the hard palate, and by the epiglottis pro- 
jecting upward from below. The glottis is open and the 

156 



Digestion in the Stomach. 



l S7 



gullet is closed. Air enters the nostrils, passes along the 
nasal passages above the hard palate, back of the soft 
palate and epiglottis, through the open glottis into the 
windpipe, and on to the lungs. 

The Process of Swallowing. — When the morsel of food 
is ready to be swallowed the tongue pushes it back into 
the pharynx ; the soft palate is raised to shut off the 
passage into the nasal cavity ; the epiglottis is pulled down 




Eustachian Tube 
Soft Palate, Raised 
Food 



-Epiglottis, Down 
Gullet, Open 

-Glottis, Closed 



Fig. 71. Positions of the Organs of the Mouth and Throat during Swallowing. 

over the glottis, or opening of the windpipe; and the base 
of the tongue extends back over the epiglottis; thus the 
air passages, above and below, are shut off, and the food 
passes over the epiglottis into the gullet. The muscles of 
the pharynx also do their part in pushing the food along. 
As soon as the food has passed over the epiglottis, the 
epiglottis rises to its upright position, and the soft palate 
drops back to its place, leaving the air passages again 
open. 



158 Physiology. 

* 
Breathing and Swallowing. — It is to be observed that 
the food tube and the air tube cross, and that the pharynx 
is their crossing. As we are swallowing only a small part 
of the time, the passageway naturally stands open to the 
air; and when we swallow, the parts are, by muscular 
effort, temporarily arranged for this work. There is a 
spring switch (to borrow a term from the railway) which 
keeps the track open for the air, which is all the time 
passing ; but when the food comes along, the switch must 
close the air passage and hold open the food passage until 
the food has passed. 

Structure and Action of the Gullet. — The gullet has 
an outer muscular coat and an inner mucous coat (see 
Fig. 72). The muscular coat has two layers, an inner 
with circularly arranged fibers, and an outer layer with 
fibers running lengthwise. When the food enters the gul- 
let the muscle fibers, especially the circular fibers, shorten, 
and by a wave-like action push the mass rapidly along into 
the stomach. The first part of swallowing is voluntary ; 
but after the mouthful has entered the gullet the action is 
involuntary. The mucous lining of the gullet has many 
mucous glands which make the passageway smooth by the 
mucus which they secrete. 

Illustration of Passage through the Gullet. — The passage of the food 
through the gullet may be illustrated as follows : Let several persons 
hold a large rubber tube with their hands in contact. Put an egg-shaped 
piece of wet soap in the tube. The first hand is shut and pushes the 
soap along into the part of the tube held by the next hand ; this hand 
now compresses the tube, while the first hand remains clinched ; and so, 
in turn, the object is pushed the whole length of the tube. 

The Stomach. — Just below the diaphragm the digestive 
tube widens suddenly, forming the stomach ; the stomach 



Digestion in the Stomach. 



J 59 



is an oval sac lying just beneath the diaphragm, with the 
large end to the left and the small end to the right. The 
smaller end, by narrowing, becomes the small intestine. 
When the stomach is empty it collapses, as its walls are 
soft and flexible. When distended it may hold three pints, 
or, when greatly distended, even more. 

The Coats of the Stomach. — The stomach and intestines have four 
coats, in the following order, beginning at the outside : the peritoneum, 
the muscular, the submucous, and the mucous coats. The muscular 
coat of the stomach consists of three layers, distinguished by the arrange- 



PYLORUS 




Fig. 72. 



Longitudinal Section of Stomach, showing Gastric Glands in Position. 
(Back View. Mucous Coat unduly Thickened.) 



ment of the fibers, a circular layer, a longitudinal layer, and an oblique 
layer. The mucous lining is somewhat loosely attached to the muscular 
coat by the submucous coat between them, and when the stomach col- 
lapses, the mucous coat is thrown into folds, usually running lengthwise. 

The Gastric Glands. — In the inner surface of the mucous 
membrane are many holes. These are the mouths of the 
ducts of the gastric glands. If a duct is traced inward, it 
is found to be either a simple tube (see Fig. 73) or to divide 
into branches, usually two or three. 



i6o 



Physiology. 



The Gastric Juice. — The liquid secreted by these glands 
is called the gastric juice. The gastric juice is chiefly 
water, containing a substance called pepsin, and a small 
amount of acid. The amount of gastric juice secreted 
daily has been estimated at four or five quarts. Of course, 
we must bear in mind that nearly all of this is again 
absorbed from the digestive tube, and is not a loss to the 
body. 

Blood Supply of the Stomach. — The mucous membrane 
is well supplied with blood-tubes, but while it is resting the 

blood flow is dimin- 
MouthofGiand Epithelium ished, and it is pale. 

But as soon as food 
is introduced into the 
stomach the blood flow 
is greatly increased, 
and the mucous mem- 
brane becomes red. 
This blood supply gives 
the glands the materi- 
als with which they 
manufacture the gastric 
juice. At the same 
time the cells of the 
glands are stimulated to action, and the secretion is poured 
-out rapidly. The saliva also aids in stimulating the secre- 
tion of the gastric juice. 

The Work of the Gastric Juice. — The special work of the 
gastric juice is accomplished by the pepsin, aided by the 
acid ; these change proteids into a soluble substance, called 
peptone, which can be absorbed through the walls of the 
digestive tube into the blood. 




Connective Tissue 
Fig. 73. Three Glands of the Stomach. 



Digestion in the Stomach. 161 

Rennet and Rennin. — Rennet, used in cheese making, is a familial 
substance obtained from the fourth stomach of the calf. When milk 
enters the stomach it is curdled ; that is, the casein previously dissolved 
in the liquid milk is curdled. This curdling, or coagulation, is caused 
by a substance in the gastric juice called rennin. 

The Action of the Stomach. — At the same time all the 
food is soaked by the gastric juice, the process being 
greatly assisted by the churning motion of the stomach 
caused by the action of the muscular coat. This muscular 
action of the stomach is called the peristaltic action. The 
food is thus gradually reduced to a pulpy mass called 
chyme. During the first part of digestion in the stomach 
the thick ring of circular fibers, called the pylorus (gate- 
keeper), around the opening from the stomach into the 
intestine, keeps the passage nearly closed, leaving a small 
hole for liquids only. But as the food is reduced to the 
proper condition the muscles relax and allow the chyme to 
pass into the intestine. And at last any indigestible sub- 
stances are usually allowed to pass. 

Sphincter Muscles. — Such rings of muscular fibers as 
the pylorus, guarding openings, are called sphincter 
muscles. 

Time of Stomach Digestion. — The time required for the 
stomach digestion of a meal is from three to four hours, 
though this may be much longer if very indigestible sub- 
stances have been eaten, or if the condition of the body 
or mind is such as to retard the process of digestion. 

Chyme. — The rest of the food, now called chyme, is 
passed on into the small intestine. It is acid, and in a 
liquid or semiliquid condition. Chyme,> as it enters the 
intestine, is a mixture of digested, partly digested, and 
undigested materials. Some of the starch has been changed 



1 62 Physiology. 

to sugar, but only a small part, owing to the short time of 
mastication. The bulk of the starch is unchanged. Some 
of the proteid is already changed to peptone. Part is still 
proteid, while part is in an intermediate stage between 
proteid and peptone. Fat is melted by the heat of the 
mouth and stomach, and is more or less divided into small 
drops by mastication and the movements of the stomach. 
For instance, in eating bread and butter, the melting butter 
will be finely mixed with the bread as it is chewed. The 
water in the chyme was partly taken as such, and partly 
derived from the saliva and gastric juice. There are also 
present ptyalin, pepsin, mucus, salts, and some indigestible* 
substances. At intervals the sphincter muscles of the 
pylorus relax, and the contractions of the stomach send the 
liquid mixture into the intestines by spurts. 

Heart-burn. — Heart-burn is a burning feeling in the 
stomach and lower part of the chest caused by indigestion. 
There is a fermentation in the stomach, usually producing 
an acid or sour stomach. 

Summary. — i . The pharynx opens into the mouth, nostrils, wind- 
pipe, and gullet. 

2. In breathing, air passes through the nostrils and the pharynx, 
and enters the windpipe ; the soft palate is down and the epiglottis 
is up. 

3. In swallowing, food passes from the mouth, through the pharynx, 
into the gullet ; the soft palate is raised and the epiglottis is pressed 
down, covering the opening into the windpipe. 

4. Food is pushed along the gullet by the shortening of the ring- 
like muscles. 

5. The stomach is pear-shaped, with the large end to the left. 

6. The stomach has four coats, — serous, muscular, submucous, and 
mucous. 

7. The gastric glands are tube-like pits in the mucous coat of the 
stomach. They make gastric juice. 



Digestion in the Stomach. 163 

8. The mucous coat of the stomach contains more blood during 
digestion, and is more red, than when resting. 

9. Pepsin in the gastric juice changes proteids to peptones. 

10. The muscles of the stomach wall give a churning motion. 

11. The food is reduced to a thick liquid called chyme. 

12. The stomach requires three or four hours to digest a meal. 

Questions. — i. Why is one more likely to choke if he thinks about 
the process of swallowing? 

2. What are the peculiarities of a cow's stomach? 

3. What is the "rice ordeal 1 ' ? What can we learn from it? 

4. Why do athletes eat sparingly before a game? 

5. How does indigestion sometimes rnake one short-winded? 

6. Why is it uncomfortable to hold the organs in the " swallowing 
position 1 '? 

7. Why is it hard to swallow a pill? Why take water with it? 

8. Try swallowing repeatedly. Why is it difficult? 

9. How is the structure of the windpipe favorable to swallowing? 
10. Why is indigestion more noticeable in the stomach than later? 



CHAPTER XVII. 

DIGESTION IN THE INTESTINE. 

The Parts of the Intestine. — The intestine consists of two 
parts : first, the long and narrow small intestine ; second, 
the short and wide large intestine. (See' Fig. 76.) 

The Small Intestine. — The small intestine has essentially 
the same structure as the parts of the digestive tube already 
studied; namely, a muscular coat and a mucous lining. The 
muscular coat has two layers, one of circular and the other 
of longitudinal fibers. The muscular coat mixes the juices 
with the food and moves it along. The muscular action 
of the intestines is a slow writhing motion, called peristaltic 
action. The mucous coat supplies mucus, which keeps 
the surface soft and smooth. 

The Liver. — The liver is just under the diaphragm. It 
is convex above, where it fits the hollow under surface of 
the diaphragm, and hollow below, where it fits over the 
upper surface of the stomach. The greater part of it is 
on the right, as the greater part of the stomach is on the 
left, side of the body. The liver is dark colored and of 
very delicate structure, chiefly because it has very little 
connective tissue. It is the largest gland in the body, 
weighing nearly four pounds. 

Bile. — Bile is a bitter, golden red, or sometimes greenish 
yellow, liquid made by the liver from the blood. About 
two and a half pints of bile are made daily. 

164 



Digestion in the Intestine. 



r6 5 



The Bile Sac. — This is a sac of about the size and shape 
of a pear, and is attached to the under surface of the liver. 
It has a duct, the bile duct, which empties into the small 
intestine a few inches beyond the stomach. Part of the 



Parotid Sali- 
vary Gland 

Gullet 



Precaval Vein 
Postcaval Vein 



Sublingual 
•Salivary Gland 



Submaxillary 
•Salivary Gland 




Hepatic Vein- 



Mesenteric 
Vein 



Mesentery 



Intestine 
Fig. 74. The Organs which change Food into Blood. 

bile is at once poured out into the intestine, but part, 
especially when we are not digesting, is stored in the bile 
sac, to be poured out during digestion. 

Functions of Bile. — i. It aids in emulsifying the fats. 
2. It aids in the absorption of fat. . 



1 66 Physiology. 

3. The bile, to a certain extent, is waste matter ; so the 
liver is an organ of excretion as well as an organ of secretion. 

4. It is found that if, for any cause, the bile is prevented 
from entering the intestine, constipation follows, and the 
contents of the large intestine have a much more fetid 
odor than usual. The bile retards this putrefaction. 

The Pancreas. — Just back of the stomach is another im- 
portant gland, the pancreas. It is a pink organ, weighing 
three or four ounces and having the shape of a dog's 
tongue. It has a duct which empties into the small intes- 
tine at the same point where the bile enters, but it has no 
sac in which to store the liquid which it secretes. It takes 
from the blood certain materials and makes a liquid called 
pancreatic juice. 

Pancreatic Juice. — This is a clear, sticky liquid, very 
much like saliva in appearance. Although the pancreas is 
a small organ, its work is very important. It gets a large 
blood supply and makes a large amount of pancreatic juice. 
The pancreas of calves is often eaten, being known by the 
name " sweetbread." 

The Work of the Pancreatic Juice. — The pancreatic juice 
acts on all the principal classes of foodstuffs : — 

1. A substance in it called amylopsin acts on starches, 
changing them to sugar even more actively than the ptyalin 
of the saliva. 

2. Another substance in pancreatic juice is trypsin ; like 
the pepsin of gastric juice, it changes proteids to peptones. 

3. The pancreatic juice also emulsifies the fats. The 
fat is divided into exceedingly fine drops, each covered 
with a coating of albumen. An emulsion can be made 
artificially by shaking together water, oil, and white-of-egg, 



Digestion in the Intestine. 167 

The shaking breaks the oil into fine drops, which would 
soon gather again if no other substance were present ; but 
the albumen forms a thin coating around each droplet, 
enabling it to remain distinct in the liquid. 

The Intestinal Glands. — The mucous membrane of the 
small intestine has an immense number of tube-like glands. 
(See Fig. 78.) Their structure is 
much like that of the gastric glands 
shown in Fig. 73. Fig. 75 shows 
them as seen when cut across. 
These glands make a liquid called 
intestinal juice, which completes the 
work of the other digestive liquids. 

Review of Digestive Liquids. — 

Saliva acts only on starch, gastric 

juice on proteids, bile on fats; but at^gSSZgSS 

pancreatic mice acts on all three. the intestine, showing intestinal 

1 J Glands in Transverse Section. 

„,« « * • r^i . (Highly magnified.) 

The Large Intestine. — This con- 
sists mainly of the colon, the final portion being called the 
rectum. 

The Colon. — The small intestine joins the colon near the 
lower right side of the abdomen. Where the small intes- 
tine enters the colon there is a valve which keeps the 
material from coming back into the small intestine. The 
colon runs upward on the right side (ascending colon), 
crosses over to the left side (transverse colon), and descends 
on the left side (descending colon), and, after curving some- 
what like a letter S, becomes straight again, this part being 
called the rectum. It is well to know the course of the 
lower bowel, as pressure may be so applied as to push the 
contents along in case the bowels become torpid. (Fig. 76.) 




i68 



Physiology. 



Gullet 



Stomach 
Duodenum 



Review of the Digestive Tube. — The whole digestive 
tube may be briefly and roughly described as a muscular 

tube of varying diameter, 
lined by mucous mem- 
brane. The muscular coat 
pushes the contents along 
and mixes them with liq- 
uids ; the mucous coat is 
beset with glands, making 
liquids, some of which 
merely soak the food, 
others act on it chemically, 
I while mucus serves to 
| make the surface slippery, 
o It seems that these myriads 
° of simple glands are not 
enough, so several large 
compound glands lie along- 
side the food tube and 
empty their secretions into 
it by ducts;, these com- 
pound glands are the sali- 
vary glands, the pancreas, 

Fig. 76. The Stomach and Intestines. anc * the liver. 




Vermiform 
Appendix 



Rectum 



Length of the Intestine. — The length of the small in- 
testine is about twenty-five feet, and of the large intestine 
five or six feet. The large intestine is not a direct contin- 
uation of the small ; that is, the small intestine opens at a 
right angle into the large near the beginning of the latter, 
so that there is a short blind end called the cecum (see 
Fig. 76). In some animals this is large and has consider- 
able length, but in man it is very short. There is a closed 



Digestion in the Intestine. 169 

prolongation of the cecum, the vermiform appendix. This 
appendix is frequently the seat of serious or fatal inflam- 
mation, called appendicitis. This disease is not usually 
caused by the lodging of seeds in the cecum, as most 
people suppose ; still it is better not to swallow such things. 

A Simple Gland. — A gland is a structure which takes 
liquid from the blood and pours it out on some surface. 
In its simplest form a gland is a mere pit, or hole, such as 
the gastric glands, shown in Fig. 73. The blood capilla- 
ries give off lymph around the gland, and from this lymph 
the cells of the gland take their material. A sweat gland 
needs more length than a gastric gland, and the extra 
length is coiled up in a ball at the inner end. Many 
small glands are forked at their inner ends, thus increas- 
ing their surface. 

Kinds of Glands. — Fig. 77 shows different forms of 
glands, from the simplest to the most complex. In the 
compound glands the lining of the duct, which is merely 
a passageway, is different from the rest of the gland. 
Glands that take waste matter from the blood are called 
excretory glands, such as sweat glands ; they do not usu- 
ally make much change in the material. Such glands as 
the gastric glands change the material that they pour out; 
the gastric juice is different from anything found in the 
blood. Such glands are called secretory glands. Sweat is 
an excretion ; gastric juice is a secretion. Still, all glands 
are said to secrete, that is, to separate something from the 
blood. And gland action in general is called secretion. 
In structure, then, glands may be simple or compound. 
In function they may be excretory or secretory. 

Control of Glands. — All glands are under the control 
of nerves. But this control is involuntary, and under the 



170 



Physiology. 



management of the sympathetic nervous system. The 
mouth may " water" for some attractive food, or become 
dry through fear or anxiety. Hence we can see why a 
restful, contented condition of mind and body will be 
likely to favor the action of the many glands along the 
digestive tube ; and, on the other hand, why anxiety or 
fretfulness are likely to hinder their action. 



Epithelium or Epidermis. 




Compound Glands 
Fig 1 , 77. Simple and Compound Glands. 

Summary. — 1. The intestine has two coats, an outer, muscular, and 
an inner, mucous, coat. 

2. The intestine consists of two parts, the small intestine and the 
large. 

3. The liver is the largest gland in the body. It secretes bile, which 
is stored in the bile sac. 

4. Bile aids in emulsifying and absorbing fats, and retards putre- 
faction. Bile is partly waste matter. 

5. The pancreas is a small tongue-shaped organ back of the 
stomach. It secretes the pancreatic juice. 



Digestion in the Intestine. 171 

6. Pancreatic juice acts on proteids, fats, and starch. 

7. In the walls of the intestine are many small intestinal glands. 
Their secretion helps complete the process of digestion. 

8. The main part of the large intestine is the colon. It has three 
parts, ascending, transverse, and descending. The last part of the 
intestine is the rectum. 

9. The small intestine is twenty-five feet long, the large, five or six. 

10. A gland is a hollow structure that secretes a liquid from the 
blood. 

11. Glands are simple, like an intestinal gland, or complex, like the 
pancreas. 

12. Glands are excretory, such as the sweat glands, or secretory, 
such as the gastric glands. 

Questions. — i. Why is there such a difference in the lengths of 
intestine in the cat and the cow? 

2. What is biliousness? 

3. Why is the pancreas sometimes called the "abdominal salivary 
gland"? 

4. Why does digestion proceed more slowly in the intestine than 
in the stomach ? 

5. In what direction should the abdomen be rubbed to assist a 
movement of the bowels? 



CHAPTER XVIIL 

ABSORPTION. 

Absorption a Living Process. — The layer of cells which 
forms the inner surface of the mucous membrane is called 
epithelium. These cells are moist, soft, and thin-walled. 
They take up the digested foods, now in liquid form, and 
pass them on to the lymph and so into the blood capillaries 
that are thickly distributed just beneath the surface. 

Absorption from the Mouth. — Sugar, and some other 
substances, may be absorbed by the mouth as soon as it is 
dissolved. But very little material is thus absorbed. 

Absorption from the Stomach. — Some parts of the food 
that are already digested, or such matters as are soluble, 
e.g. water containing sugar, peptone, salts, etc., may be 
absorbed immediately through the walls of the stomach 
into the blood capillaries. Recent experiments show, how- 
ever, that the amount of absorption from the stomach is 
much less than was formerly supposed; water, for instance, 
" when taken alone, is practically not absorbed at all in the 
stomach. As soon as water is introduced into the stomach 
it begins to pass out into the intestine, being forced out in 
a series of spurts by the contractions of the stomach." 

Absorption from the Small Intestine. — Most of the 
digested food is absorbed in the small intestine. 

Increased Surface for Absorption. — The mucous mem- 
brane of the small intestine is thrown into ridges, but, 
unlike those of the stomach, they run crosswise. Again, 

173 



Absorption. 



173 



ViMuses 



while the folds in the lining of the stomach are temporary, 
these are permanent. They increase the surface of the 
lining and retard the passage of the food material, and so 
aid the process of digestion and of absorption. 

Villuses. — To increase, still further, the surface for 
absorption, the mucous membrane of the small intestine is 

thickly covered with 
little cylindrical pro- 
jections, like the 
"pile" on velvet. 
Each of these pro- 
jections is a villus. 

Intestinal Glands ^B 

Structure of a Vil- 

A villus is 
about a thirtieth of 
an inch long. It is made up of four parts : (1) on the out- 
side a layer of soft, moist, thin-walled cells; (2) plain 
muscle fibers, running lengthwise; (3) a network of blood 




Fig. 78. Mucous Membrane of Small Intestine, showing lug. 
Intestinal Glands and Villuses, greatly Magnified 




Lacteal with Valves Capillaries 



Muscles 



Epithelium 



Fig. 79. Four Parts of a Villus, greatly Magnified. 

capillaries ; and (4), near the center, lymph capillaries, 
called lacteals. Fig. 79 shows these four parts separate, 
while Fig. 80 shows them combined, as they are in the 
complete villus. 



174 



Physiology. 



Absorption by the Villuses. — The digested food is in 
liquid form and surrounds the villuses. The three main 
substances to be absorbed are peptones, sugar, and fat. 
The outer cells of each villus absorb these and pass them 
inward. The peptones and sugars are taken into the blood 
capillaries, while the fats enter the lacteals. 

Muscular Action of the Villuses. — In each villus there 
are plain muscle fibers. When these shorten they squeeze 
the chyle, that has already been absorbed, into the lymph 
tubes of the wall of the intestines, and on into the main 



Tntcnna^p 




[^...-Epithelial Covering 



Lacteal 

Longitudinal Mus- 
cular Fibers 
Capillary Network 



Fig. 80. A Complete Villus, very greatly Magnified. 

lymph duct. The chyle cannot return to the lacteal when 
the muscles relax, on account of the valves, similar to 
those of the veins, in the lacteal at the base of the villus. 
Then, when the muscles relax, the lacteal is empty, and 
ready to absorb more of the emulsified fat that we call 
chyle. This action also helps the flow in the blood 
capillaries. 

The Lacteals and Lymphatics. — While the main work 
of the lymphatics, as we have seen, is the carrying of 
lymph from the tissues of the body to empty into the 
veins of the neck, the lymphatics of the intestines have 
another important function. They absorb and carry the 
fatty portions of the digested food into the general circu- 
lation. During most of the time the thoracic duct and 



Absorption. 



*75 



the lymphatics of the intestines would hardly be noticed 
because they are filled with the clear lymph. But after 



Right Lymph Vein . 




Junction of Thoracic 
Duct with Left Sub- 
clavian Vein 



Main Lymph Vein 
(Thoracic Duct) 



Intestine 



Lymphatic Glands 



Fig. 81. Lymph Veins (Lymphatics). 



absorption of fatty matter they are filled with a white 
liquid, called chyle, and are easily seen. (See Fig. 81.) 

The Portal Circulation. — All the veins coming from the 
stomach and intestines unite to form a large vein that goes 
to the liver ; this is the portal vein. When the portal vein 
enters the liver it does what veins do not do elsewhere in 
the body, — it divides into smaller branches. This division 



176 



Physiology. 



and subdivision goes on till the portal vein forms capil- 
laries branching all through the liver. 

The blood from these capillaries collects again in veins, 
which unite in one vein, the hepatic vein, which carries 
the blood into the postcaval vein just under the diaphragm. 




Fig. 82. Diagram of Portal Circulation. 

Going back again to the beginnings of the portal vein, 
it is clear that it starts from the capillaries of the stomach 
and intestines. And these capillaries, as we have just seen, 
absorb the peptones and sugars. The sugars and peptones, 
therefore, go directly to the liver after being absorbed. 

Double Blood Supply to the Liver. — The liver also re- 
ceives blood from the hepatic artery, a branch of the aorta. 



Absorption. 



177 



Thus the liver gets blood from two sources, the portal vein 
and the hepatic artery, but is drained by one vein, the 
hepatic vein. 

Work of the Liver. — We have seen that the liver makes 
bile. The liver also makes another substance out of the 
blood that passes through it. This is glycogen, or " animal 
starch." It is also called " liver sugar," as it gives to liver 




Mesenteric 
Lymph Veins 
(Fats) 



Lacteals 



Capillaries 



Fig. 83. Plan of Absorption. 

a sweetish taste. Glycogen is given back to the blood and 
carried away by the hepatic vein to the body, where it 
serves as food to the tissues. 

Routes of Different Foods after Absorption. — There are, 
then, two routes taken by the food after absorption. The 
peptones and sugars go to the liver through the portal 



178 



Physiology. 



vein, while the fats are carried by the main lymph duct or 
thoracic duct. These two streams unite before reaching 
the heart. The fats pass around the liver, instead of 
through it as do the peptones and sugars. 



PARTS 

OF 

DIGESTIVE 

TUBE. 


MECHANI- 
CAL PRO- 
CESSES. 


GLANDS. 


LIQ- 
UIDS. 


CHEMICAL 
CHANGE. 


ABSORPTION. 


Material 


By 


Mouth. 


Cutting 

and 

Grinding. 


Salivary. 


Saliva. 


Starch 

to 
Sugar. 






Pharynx. 


Raising Soft 

Palate. 
Depressing 
Epiglottis. 












Gullet. 


Food carried 
to Stomach. 


Mucous. 


Mucus. 








Stomach. 


Churning 

and 
Mixing. 


Gastric. 


Gastric 
Juice. 


Proteid 

to 
Peptone. 


Water. ^ 
Salts. 1 
Sugars. 
Peptones, j 


Blood 
Capillaries. 


Small 
Intestine. 


Mixing 

and 

Moving 

Food. 


Liver. 
Pancreas. 

Intestinal. 


Bile. 

Pancreatic 

Juice. 
Intestinal 

Juice. 


f Starch to Sugar. 
j Proteid to Peptone, 
j tj. j Emulsified. 
t ' Decomposed. 


Water. ] 
Salts. 1 
Sugar. j 
Peptone. ! 
Fats. 


Blood 
Capillaries. 

Lacteals. 


Large 
Intestine. 


Food 
Forced on. 


Mucous. 


Mucus. 




Water. 





Fig. 84. Outline of Digestion and Absorption. 

Amount of Liquid Absorbed. — It is estimated that there 
is poured into the digestive tube daily one quart of saliva, 
four or five quarts of gastric juice, one quart of bile, and 
about a quart of pancreatic juice. If the food and drink 
amounts to two quarts, there must be more than two gal- 
lons of liquid absorbed from the digestive tube each day. 



Absorption. 179 

The Work of the Large Intestine. — Most of the ab- 
sorption is accomplished in the small intestine ; but as the 
food passes on into the large intestine the work of digestion 
and of absorption is carried somewhat farther. If the 
residue be not soon expelled, there may be absorption of 
some of the results of putrefactive changes, and a sort 
of general poisoning of the whole body. Hence the 
great importance of regularly and thoroughly emptying 
the lower bowel. The matter thus expelled is largely 
made up of indigestible material, with some real waste 
substances. 

Taking up again our comparison of the body and a 
stove, we see that the feces are not true waste products, 
but are rather clinkers, or material that has not been 
burned or oxidized in the body. The real wastes of the 
body are the carbon dioxid, urea, water, etc., that are pro- 
duced by the oxidation of the tissues, and are mostly thrown 
off by the lungs, kidneys, and skin. 

Summary. — 1 . The cells lining the digestive tube take up the 
digested food, now in liquid form, and pass it into the lymph. 

2. There is some absorption, from the stomach, of sugar and 
peptone. Most of the absorption is from the small intestine. 

3. The hair-like villuses greatly increase the absorbing surface. 

4. A villus has four parts, the outer layer of cells, plain muscle 
fibers running lengthwise, blood capillaries, and lacteals. 

5. The outer cells of the villus take up the liquefied food. 

6. Sugar and proteids enter the blood capillaries ; fats enter 
the lacteal capillaries. 

7. The muscles of the villus pump the liquids along and aid 
absorption. 

8. The lacteals are part of the lymph system of the body. They 
absorb and carry fats. 

9. The veins from the stomach and intestine join to form the por- 
tal vein which enters the liver. Here it breaks up into capillaries. 



l8o Physiology. 

10. The liver has two supplies of blood, from the portal vein and 
the hepatic artery. It is drained by one vein, the hepatic vein. 

11. The liver makes bile and glycogen. 

12. Sugars and proteids go through the liver; fats pass around the 
liver through the main lymph vein, or thoracic vein. 

13. There are over two gallons of liquids absorbed daily. 

Questions. — 1. Why is it best to begin a hearty meal with soup ? 

2. Why should the liver receive so much blood ? 

3. What is the meaning of " biliousness " ? 

4. What is the advantage of a " fruit diet " ? 

5. Why does active exercise tend to keep the bowels open? 



CHAPTER XIX. 

HYGIENE OF DIGESTION. — NUTRITION. 

Digestion and Circulation. — During digestion there must 
be a large supply of blood in the digestive organs. It is 
needed both to supply the material for the glands to make 
the digestive liquids and also to absorb and bring away the 
newly digested food. Therefore, during digestion there 
must be less blood in other parts of the body. 

Digestion and Muscular Work. — If one exercises actively 
immediately after eating, the process of digestion will be 
interfered with, because the blood will be drawn away 
from the digestive organs to the muscles. It is well to 
rest for a short time after eating a full meal. 

Digestion and Study. — For the same reason it is better 
not to begin hard study immediately after a full meal. The 
blood needed for the work of digestion will be called to the 
brain, and digestion will suffer. 

Solid Foods digest Slowly. — If a very hungry person 
begins his dinner with solid food, he is likely to eat too 
fast. Hunger is a demand of the system for food. It 
takes some time for solid food to go through all the pro- 
cesses of digestion, and be absorbed into the system and 
satisfy hunger.- 

Value of Soup. — But if the meal begins with soup, which 
is readily absorbed, the demand of the system will begin to 
be met, and there will not be the same tendency to rapid 

181 



1 8 2 Physiology. 

eating. Further, a warm soup stimulates the blood flow in 
the mucous membrane, and thus prepares for more thorough 
digestion. 

Desserts. — Dessert and sweetmeats, following a meal, 
are often helpful by further stimulating the secretion of the 
glands. Nuts, which are not very digestible, are beneficial 
if eaten sparingly, The agreeable taste stimulates the 
salivary glands, and the saliva stimulates the gastric glands 
to increased activity. The danger in taking dessert is that 
the pleasing taste tempts us to continue eating after we 
have had enough. Pie is usually hard to digest. 

The Bad Effects of Imperfect Mastication. — If we swallow 
food before it is thoroughly ground and mixed with the 
saliva, the stomach and other parts of the digestive organs 
will require much more time to reduce the food to a liquid 
form. Further, when eating hastily, we are very apt to 
eat too much. Thus we may give the stomach a double 
amount of material to handle, and the material may not be 
half so well prepared as it should be. Of course the organs 
suffer and break down if this treatment is continued. 

Effect of Repose on Digestion. — Not only mastication, but 
the whole process of digestion, goes on better when the 
body and mind are at rest and in a peaceful condition, as 
all the glands are under the control of the nervous system, 
and are greatly influenced by the condition of the body. 
During a meal, and for a short time before and after, all 
thoughts of one's occupation, and especially all anxiety, 
should be dismissed from the mind. For those whose 
digestion is not strong, it is desirable to rest after each 
meal. 

Conversation at Meals. — During a meal there should be 
conversation on topics of general interest. Talking at the 



Hygiene of Digestion. 183 

table also makes us more deliberate in eating. " Chatted 
food is half digested." 

Time of Eating. — The American custom of three meals 
a day -corns well adapted to the needs of our people. The 
best time for the chief meal is near the middle of the day, 
as is the custom in the country ; for the bodily powers are 
higher than later in the day. But for city people, and 
others who are very busy in the middle of the day, it is 
undoubtedly better to take the chief meal after the rush of 
the day's work is over, when there is time for a deliberate 
meal and when the mind is free from business cares. In 
many homes this is the only time when the whole family 
can leisurely meet at the table. 

Eating between Meals. — The stomach should have time 
to rest and prepare for the work of digesting another meal. 
Many find two meals a day sufficient. There are some 
persons, however, for whom it would be better to have 
more meals, with less food at a time. Meals should be 
regular. 

Amount of Food Needed. — This varies greatly with the 
individual, age, the kind and amount of labor, etc., so that 
no very helpful rule can be given. Each person must find 
by experience what is best for himself. It is the opinion 
of many leading physicians that the majority of mankind 
eat too much. 

Intemperance in Eating. — "I have come to the conclu- 
sion that more than half of the disease which embitters the 
middle and latter part of life is due to avoidable errors of 
diet ; and that more mischief, in the form of actual disease, 
of impaired vigor, and of shortened life, accrues to civilized 
man from erroneous habits of eating than from the habitual 



184 Physiology. 

use of alcoholic drink, considerable as I know that evil to 
be." — Thompson. 

Self-denial in Eating. — It is a good old saying, "We 
never repent having eaten too little." Nearly every one 
has regretted having eaten too much. It is better to 
stop before one has eaten quite as much as he would 
like, especially when taking highly-seasoned or sweetened 
food. 

Fat as a Tissue. — As a tissue fat serves as a stored-up 
food. A fat person can endure starvation longer, other 
things being equal, than a thin person. A layer of fat 
under the skin serves also as a heat saver. 

Hibernation. — Hibernating animals are fat when they enter upon 
their winter sleep, but are lean when they come out in the spring. 
Remaining inactive, they have produced very little energy, their only 
motions being a slow and feeble breathing and heart-beat. They have 
consumed the fat, using it mainly in maintaining the necessary heat. 
In short, they have burned their fat to keep them warm. 

Importance of Renewal of Blood and Lymph. — The 

lymph surrounds the individual cells which make up the 
tissues of the body. Every cell lives an independent life, 
to a certain extent, taking its nourishment directly from 
the lymph around it. The importance of an abundant 
supply of good lymph is apparent. The supply and renewal 
of the lymph depends on the blood. 

Effect of Digestion on Blood and Lymph. — If digestion is 
not good, or if there is not enough good food, good blood 
cannot be made, and the lymph will not be good. The 
cells are more or less starved, or poisoned if wastes are not 
properly removed, and the general tone of the body will 
soon be lowered; for the health of the body as a whole 
depends on the average condition of the cells composing 



Hygiene of Digestion. 



i8 5 



the body, just as the condition of any community depends 
on the average condition of the individuals of that com- 
munity. 

Assimilation. — The formation of tissue from the mate- 
rials brought by the blood is assimilation. It is the last 
step in building up the tissues. 



Capillaries 



Vein 



Artery 




Artery 



Capillaries 
Fig. 85. Diagram of the Heart and Blood Tubes (Back View*, 



Blood a Mixture of Good and Bad. — In the blood streams 
are combined the good and the bad. The newly digested 
food is received into a current of impure blood in the post- 



13 — PHY 



86 



Physiology. 



caval vein. The blood from the kidneys, probably the 
purest blood in the body, joins the same impure stream. 
From the aorta, red blood, usually called pure, — the same 



Lung Capillaries 



Pulmonary Vein 




Pulmonary Artery 

Right Auricle 
Right Ventricle 

-Cava) Vein 



Body Capillaries 

Fig. 86. Plan of Circulation, representing the Right and Left Halves of the Heart sepa- 
rated, showing that the Blood makes but One Circuit. 



kind that goes to the brain, — is sent to the kidneys and to 
the skin to be purified. Yet, as this mixed blood flows 
through each organ, that organ, so long as it is in health, 
takes from it only what it should take. 



Hygiene of Digestion. 187 

Action of Diseased Kidneys. — The kidney takes, during 
health, only the waste matters, leaving the valuable nour- 
ishing material. But, in disease, the kidneys may take out 
some of the most valuable nourishing material. Suppose 
that in a mill, a workman, whose business is to shovel out 
wastes, becomes crazy, and shovels wheat or flour out of 
the mill into the stream below. The diseased kidney may 
be said to have become crazy, and in the disease called 
"diabetes" throws out sugar, and in " albuminuria' ' ex- 
cretes albumen. 

Blood Streams like Water Pipes and Sewer Combined. — 

It is as though the water supply of a city house was taken 
from the sewer ; each organ needing a supply of building 
material acts like a filter, taking from the blood what it 
needs, paying no attention to the impurities present, and 
the organs of excretion select the impurities, allowing the 
useful substances to pass on to the places where they are 
needed. Figs. 85, 86, and 87 show what the blood stream 
gives to each of the organs of the body and what it takes 
from them to throw out as waste matter. 

How the Body Changes. — The body is continually 
changing, new material from the digested food taking the 
place of the worn-out tissues. It is a common saying that 
the body changes once in seven years. But while the 
more active tissues, such as muscle, must change many 
times in a year, we know that the teeth do not grow after 
they are once formed. 

The Body like an Eddy. — The changes in the body have 
been compared to an eddy in a stream. The form of the 
eddy remains the same, while particles of \vater are enter- 
ing on one side and leaving on the other. In a short time 



1 8 8 Physiology. 

all the particles are changed. But in the body the more 
permanent parts change slowly. 

Nutrition. — Nutrition includes all the changes that take 
place in the body from the reception of food to the excre- 
tion of the waste matter. It includes digestion, absorption, 
circulation, assimilation, respiration (oxidation), and excre- 
tion. The first four of these processes are stages in build- 
ing tip the tissues ; the last two are process of tearing down. 

We cannot destroy Matter. — When a stick of wood is 
burned it is no longer wood. But the matter is not de- 
stroyed. It could all be obtained again from the smoke 
and ashes. So, in the continual wasting away of our 
bodies, there is no real loss of matter. Our weight is re- 
duced, but the wastes are still part of the earth or the air, 
and are of use in the world. We are as unable to destroy 
matter as we are to create it. 

The Ceaseless Round of Matter. — A particle of carbon 
in the carbon dioxid of the expired breath may be taken in 
by a blade of grass. A cow eats the grass, and we may 
before long take the very same particle of carbon in the 
milk or the flesh of the cow. Or the particle of carbon 
may become part of a grain of wheat, and be made into 
flour and be eaten as bread and be a part of the body 
once more. Thus, there is a ceaseless round of matter 
into and out of our bodies. No one has a monopoly of 
any portion of matter ; it is now ours, now some one else's. 

We cannot create Force. — We get our energy from the 
food we eat, just as an engine gets its energy from fuel. 
This is saying nothing against the superiority of the 
human body and is not in the least degrading. We are 
living, growing, self -directing, and self -maintaining ma- 



Hygiene of Digestion. 189 



PULMONARY VEIN 
LEFT AURICLE 



LEFT VENTRICLE 



PULMONARY ARTERY 

RIGHT VENTRICLE 

RIGHT AURICLE 




Fig. 87. The Circulation and the Work of the Blood 



190 Physiology. 

chines. Still, starvation soon puts an end to our ability 
to produce energy of any kind. 

How we depend on Plants. — The larger part of our food 
is vegetable. And the animal foods, such as meat, milk, 
cheese, butter, eggs, etc., were made by the animals from 
vegetable matter. We are, therefore, directly or indirectly, 
dependent on plants for all our food. On the other hand, 
plants use as their food considerable of the waste matter 
thrown off by animals. 

Summary. — 1 . During digestion a large supply of blood is required 
in the digestive organs. 

2. Muscular work, immediately after eating, interferes with digestion 
by calling the blood away to the muscles. 

3. Hard study, right after a hearty meal, hinders digestion in the 
same way. 

4. Soup is a good beginning of a hearty meal, as it is more readily 
absorbed than solid food. 

5. Desserts, in moderate quantity, are useful in stimulating the 
glands which supply the digestive liquids. 

6. Hot drink at meals aids weak digestion. 

7. Imperfect mastication leads to eating too much, and throws too 
much work upon the other organs of digestion. 

8. A calm condition of the nervous system favors digestion. 

9. Conversation on cheerful topics is favorable to digestion. 

10. Three meals a day are best for most persons. 

1 1 . For persons hurried in the middle of the day it is often better 
to take the chief meal at the close of the day's work. 

12. Meals should be regular, and one should not eat between meals. 

13. There is much intemperance in eating. 

14. Fat, as tissue, is stored food. 

15. The cells depend on the lymph for their nourishment, and the 
lymph is supplied by the digested food. 

16. The blood is a mixture of good and bad material; each organ, 
in health, selects from the blood what it needs, the tissues taking 
nourishment, and the organs of excretion removing the waste 
matters. 



Hygiene of Digestion. 191 



17. Diseased kidneys may remove valuable nourishing materials 
from the blood. 

18. The body keeps changing, taking new matter to replace worn- 
out tissue. 

19. Nutrition includes digestion, absorption, circulation, respiration, 
assimilation, oxidation, and excretion. 

20. We cannot destroy matter. Our waste products become part 
of earth or air. 

21. We cannot create force. We get our energy from food as an 
engine gets its energy from fuel. 

22. We depend on plants for our food. 

Questions. — i . Should a person who has studied hard try to do hard 
muscular work the same day ? 

2. What are the advantages of a "course 1 ' dinner? 

3. Which is more wholesome, dry toast or soaked toast? Why? 

4. Why do we give a horse exercise and keep fattening stock quiet? 

5. Are fat people large eaters? Are thin people light eaters? 

6. Do sweat glands ever excrete valuable material ? 

7. In Fig. 87 find what the blood gives to each organ and what it 
takes from each. 

8. Classify the organs represented in Fig. 87. 

9. Name the organs that change most rapidly. 

10. Name the organs that change most slowly. 

1 1 . What is the source from which plants get their energy? 

12. Is matter defiled in passing from one body to another? 



CHAPTER XX. 

EXERCISE AND BATHING. 

How Exercise is Beneficial. - — Exercise stimulates the 
cells to activity and renews the lymph around the cells 
both by quickening the blood flow and by pressure on the 
lymph tubes. The glands of excretion are set to work 
more actively, and the more rapid blood stream brings 
away the material to be thrown out. 

Exercise for General Health. — Exercise is not merely 
for the muscles. It quickens the action of the whole body 
by increasing cell activity. It helps clean out the system 
and clear the brain as well. It is not so much strength as 
health that we need. The ability to do our daily work, to 
do it with comfort and without any feeling of strained 
effort, is what we need. 

Exercise prolongs Life. — Many men would live longer, 
feel better, and do greater good in the world, if they took 
regular and systematic exercise. It is a shortsighted 
policy to say, "I cannot afford the time." Not to take 
time for exercise is to mortgage one's future. " He who 
does not take time for exercise will have to take time for 
illness." The latter half of every person's life ought in 
many respects to be by far the most productive of good. 
But many cut off this half, or render it less useful through 
breaking down in health as a result of violating the laws 
of health. 

192 



Exercise and Bathing. 193 

Nature's Rewards and Punishments. — Nature never 
fails to punish every violation of her laws. Her reward 
for obedience is health and the delight that accompanies it. 

Useful Exercise. — The man, woman, boy, or girl who 
has regular work that calls for muscular activity is to be 
congratulated. Duty obliges them to take regular exer- 
cise. The boy who has " chores" to do is to be envied 
rather than pitied. 

Choice of Exercise. — But many persons are so situated 
that they have no work to do. They must choose some 
exercise that is not for a directly useful purpose. In se- 
lecting exercise one should choose (1) that which is enjoy- 
able, for exhilarating exercise is much more beneficial than 
that which is taken as a necessity ; (2) exercise should be 
in the open air whenever possible. 

Forms of Exercise. — There is a great variety of forms 
of exercise from which each person can select according 
to his age, strength, etc. For active youths there are run- 
ning, jumping, wrestling, boxing, fencing, hare and hounds, 
putting the shot, putting the hammer, vaulting, baseball, 
and football. In their season come boating and swim- 
ming, skating and coasting. Suitable for both boys and 
girls are archery, basket ball, bicycling, croquet, golf, 
horseback riding, tennis, and last, but not least, walking. 
The main trouble with walking is that it is likely to be 
taken from a sense of duty and becomes mechanical. 
The good feature of most games is that there is active 
competition, which makes them so enjoyable that one en- 
tirely forgets his work for the time. He is, therefore, in 
better condition to return to his work. 

Exercise in One's Room. — In one's room he can use 
dumb-bells or Indian clubs to good advantage. There are 



1 94 Physiology. 

also various forms of " home exercisers," such as pulley 
weights, rubber bands, etc., which are valuable. After 
exercise should come a sponge bath. 

Games of School Children. — Most of the games of school 
children are excellent kinds of exercise. Cases have been 
reported of injury from excessive skipping the rope; but 
in moderate degree it is a good exercise. Tag, snowballing, 
racing, the various games of ball, jumping, hopping, and 
other games may be played on the school grounds. 

Tennis. — Tennis is a fine game and suitable for girls as well as boys. 
It has the great advantage over baseball that it does not require a large 
ground. Two can make up a game, and a little time can be better used 
than with the games requiring more players. The exercise, too, is more 
evenly distributed. There is no long waiting, as in some games, but a 
constant interchange of play, active but not severe, with almost no danger 
of injury. 

Baseball and Football. — For those who can pursue the more vigor- 
ous games of baseball and football they are admirable. All these games 
calling for great activity and strength develop manly qualities in boys, 
and do much to make them active, fearless men, men who in time of 
danger have not only strength and endurance, but well-trained muscles, 
cool heads, and brave hearts ; men who know what to do and how to 
do it in an accident, as at fires, upsetting of boats, etc. A few strong, 
cool-headed men, by their presence of mind, often stop a panic and save 
many lives when there is an alarm of fire, which often proves false. The 
Duke of Wellington said that it was on the football fields of Eton and 
Rugby that the battle of Waterloo was won. 

Boxing. — Boxing is a splendid exercise. It calls into play nearly 
every muscle of the body. Boxing makes one quick on his feet, trains 
to quick movements of the arms, trains the eye, keeps the body in an 
erect position, and especially develops the muscles of the legs and back. 
Boxing brings out the chest and shoulders. It develops the "wind," 
and keeps one in constant action. It teaches control of the temper 
more than almost any form of exercise. It develops a degree of self- 
reliance that is worth much. Like tennis, boxing calls for little appa- 



Exercise and Bathing. 195 

ratus, little space, and only two persons. In many places where ordinary 
gymnasium work is out of the question, boxing is available. It is indeed 
a M manly art," and the doctrine taught in Tom Brown's School Days at 
Rugby is as wholesome as can be given to boys to make them strong and 
active, to give them physical and moral health. 

Bicycling. — This is an excellent exercise, as it is in the open air and 
exhilarating. There is danger of over-exertion, and it is bad for one to 
yield to the temptation to make long runs. There is danger of over- 
taxing the heart. The handle bar should be adjusted to allow a fairly 
upright position. The saddle should be such as to sustain the weight 
properly. 

" Taking Cold." — So long as one is actively exercising, 
he is not likely to take cold. But if one rests in a cool 
place, especially when he is warm, he is likely to take cold. 
The application of cold to the skin causes the arteries 
(through reflex action) to become smaller. Thus when rest- 
ing in a cool place the skin becomes pale and cold. Dur- 
ing a " cold " there is fever. The regulation of the heat by 
the skin is interfered with. Waste matter is not given off 
by the skin as it should be. At the same time it is often 
noticeable that the urine is more abundant than usual. A 
cold is often associated with constipation and inactivity of 
the liver, indicating a clogged condition of the system. As 
a cold may lead to fatal lung disease, so it may be the 
beginning of disease of the kidneys that may, in the end, 
bring fatal results. 

Bathing. — One purpose of bathing is to cleanse the 
skin. For this purpose warm water is best, and it is desir- 
able to use soap, especially on those parts which are espe- 
cially exposed to contamination, such as the hands, the 
feet, the armpits, and groins. The feet should be bathed 
every night 



196 Physiology. 

Cold Baths. — Another important function of bathing is 
to strengthen the system. For this purpose cold bathing 
is better, but this should not be too long continued, and 
must be followed by a brisk friction to give the skin a ruddy 
glow. For this kind of bath a tub is not necessary, and 
hardly desirable. The water may be quickly applied by 
means of a sponge, or bath mits made of Turkish toweling, 
and the body thoroughly rubbed with a coarse towel. The 
whole process should be completed very quickly, especially 
if the room is not warm. At the beginning of a bath, cold 
water should be applied to the head and face. 

Time for Bathing. — For those who do not take a great 
deal of vigorous exercise, which keeps the skin active, 
bathing is especially valuable. The use of warm water 
for cleansing seems best adapted to the time of going to 
bed. But the best time for the cool bath is on getting up 
in the morning. 

Warm Baths vs. Cold Baths. — Prolonged warm baths 
are weakening, and probably increase a tendency to take 
cold, whereas cold bathing is one of the very best means 
of fortifying against cold, and especially against the ten- 
dency to take cold on slight exposure. For most persons 
a cool sponge bath, on rising, will act as a most excellent 
tonic ; but if it seems to produce neuralgia, it should be 
used with caution. 

Exercise of Arterial Muscles. — We have learned that 
the blood supply to any organ is regulated by the action 
of the plain muscle fibers in the walls of the small arter- 
ies. Now, when we are subject to changes in temperature 
these muscles get exercise, and one writer has well called 
the cold bath the gymnastics of the plain muscle fibers, 



Exercise and Bathing. 197 

and we can understand how the system can be trained to 
adjust itself to cold, and enabled to avoid " taking cold." 

Habit of Cold Bathing acquired Gradually. — There are 
undoubtedly many persons who do not profit by cold bath- 
ing, but probably many of these would soon adapt them- 
selves to it by beginning with tepid water and gradually 
using cooler. To bath slowly in a cold room is not safe. 
The great secret of the benefit that may be expected from 
a cold bath is to be very brisk, the whole process occupying 
only a few minutes. Many are opposed to cold sponge 
bathing, and condemn it without giving it a fair trial. 

Summary. — i . Exercise stimulates the activity of all the organs, by 
promoting cell activity and assisting excretion. 

2. Exercise should be in the open air as much as possible. 

3. Exercise is more beneficial when it exhilarates. 

4. Exercise should be taken regularly. 

5. Warm baths are best for cleansing, and should be taken at bed- 
time. 

6. Cold baths stimulate the circulation of blood in the skin, and 
serve as a tonic to the whole system. Just after rising is a good time 
for the cold bath. 

7. The cold bath fortifies against taking cold. 

Questions. — i. Should exercise be carried to the point of fatigue ? 

2. How can one avoid taking cold after exercise ? 

3. Do girls need exercise as much as boys ? 

4. What is the condition of the body during a "cold" ? 

5. How may a cold be caused ? 

6. How may a cold be cured ? 

7. How may a cold be prevented ? 

8. Why do some persons take cold more readily than others ? 

9. Why does the same person take cold more readily at one time 
than at another ? 

10. How often should a person bathe ? 

1 1 . What hour is best for sea bathing ? Why ? 



CHAPTER XXI. 

THE BRAIN. 

The Coverings of the Brain. — There are two coats of 
the brain, the dura mater, a tough membrane, adhering to 
the inside of the skull ; and the pia mater, next to the 
brain, a much thinner membrane, traversed by blood 
tubes, and dipping down into the grooves between the 
convolutions of the cerebrum. 

The Parts of the Brain. — The parts of the brain are the 
cerebrum, the cerebellum, and the spinal bulb. 

The Cerebrum. — The cerebrum consists of two lateral 
hemispheres, separated by a deep groove in the middle 
line. The surface of the cerebrum is in irregular ridges, 
the convolutions. The outside of the brain consists of 
gray matter. The inner part of the brain is white, and 
the two halves are connected by a broad band which con- 
sists of many white fibers. 

The Cerebellum. — Back of, and below the cerebrum is 
the cerebellum. It is much smaller than the cerebrum, 
and has fine transverse ridges and grooves in place of the 
convolutions of the cerebrum. It is also of a deeper color, 
a reddish gray. 

The Spinal Bulb. — The enlarged beginning of the 
spinal cord is the spinal bulb. It is white, like the rest of 
the cord. 

198 



The Brain. 



199 



The Cranial Nerves and their Functions. — 1. The 

olfactory lobes extend forward under the fore part of the 
cerebral hemispheres. They are the nerves of smell. 



Optic 2 J 

(Sight) 



Eye Motor, -csr^ 
3, 4, 6 



Auditory, 8 
(Hearing) 



Pneumogas 
trie, 10 

Hypoglossal 
12 (Tongue 
Motor) 



I, OKactory 
(Smell) 




II, Spinal 
Accessory 



Fig. 88. The Base of the Brain, showing the Origin of the Cranial Nerves. 



2. The optic nerves, or nerves of sight, join each other 
before reaching the brain. 

3. The third pair of cranial nerves controls part of the muscles of 
the eyeballs. 

4. The fourth pair also controls eye muscles. 

5. Back of these is the larger fifth pair, the trigeminal. 
This pair supplies part of the face, and sends branches to 



200 



Physiology. 



the teeth. It is the nerve affected in neuralgia of the face. 
It is the nerve of sensation for most of the head and face. 

6. The sixth pair controls eye muscles. 

7. The seventh pair are larger, and are farther back 
and outward. These are the facial nerves, and control the 
muscles of the face and the facial expression. 

Cerebrum 




Spinal Bulb 



Fig. 89. Vertical Section of Brain. 



8. The eighth, or auditory nerves, are the nerves of 
hearing. 

9. The ninth pair arise on the sides of the spinal bulb. 
They supply the back of the tongue and the pharynx, and 
are called the glosso-pharyngeal nerves. They give the 
sense of taste from the base of the tongue. 

10. The tenth pair, or vagus nerves, pass down out of 
the brain cavity, give off branches to the pharynx and 



The Brain. 



201 




Fig. 90. — Nerve Cells of the 
Gray Matter of the Brain. 



larynx, and are distributed to the heart, lungs, and 
stomach. 

ii. The eleventh pair arise in part from the spinal cord outside of 
the cranial cavity, enter the skull, and pass out again to supply certain 
muscles of the neck and shoulders. 

12. The last pair of cranial nerves, the twelfth, supplies the muscles 
of the tongue, and are called the hypoglossal nerves. 

Gray and White Matter of the Brain. 

— The gray matter of the brain is com- 
posed of cells similar to those of the 
spinal cord, while the white matter 

^ Tra> «=- of the inner part is composed of white 

fibers like those of the outer part of 
the spinal cord, or of the nerves. 

Ganglions of the Brain. — There are several masses of 
gray matter in the interior of the brain. These are the 
ganglions of the 
brain. The white 
fibers inside the 
brain connect the 
gray matter of 
the convolutions 
and these gang- 
lions with all parts 
of the body 
through the spinal Fig. 9 1 
cord. 

Functions of the Cerebrum. — The gray matter of the 
outside of the brain is the central organ of intelligent sen- 
sation and motion. The functions of volition, or willing, 
of consciousness, of intelligenc€, seem to reside in, or rather 
to depend upon the activities of, the cells of the gray 
matter of the convolutions of the cerebrum. 

14 — PHY 



Ganglions 




— Gray Matter 



Cerebrum 



Cerebellum 



Diagram of the Brain, showing the Spinal Cord, 
Ganglions, and Course of the Fibers. 



202 



Physiology. 



The Center of Sensations itself Insensible. — All sensation 
seems to be in the gray matter of the convolutions of the 
cerebrum, and yet it is itself insensible ; it may be cut and 
cause no sensation. But when the nerve impulses from the 
various parts of the body reach the gray matter of the cere- 



sight 

Smell 

Face Sensory 
Face Motions 

Taste 




erve 
— 2d Spinal Nerve 



Fig. 92. The Cranial Nerves and Sense Organs. 



brum they rouse the cells here to an activity that gives us 
what we call sensation. It is never a sensation until it 
reaches this part and is properly interpreted. 

Crossed Control of the Body. — While each hemisphere 
mainly controls the muscles of the opposite half of the 
body, it also, in part, has control of its own side. Paralysis 



The Brain. 



203 



of one side is due to injury of the opposite hemisphere of 
the cerebrum. 

Location of Brain Functions. — Much has been learned in 
late years as to the location of special functions in the brain. 



CENTRAL FISSURE 



MOTOR AREA / 




FISSURE OF SILVIUS 



Fig. 93. Location of Brain Functions. 

Some of the motor and sensory centers are shown in 
Fig. 93. 

Connection of Brain Centers. — These different brain 
centers are connected by nerve fibers, and through these 
connecting fibers we produce various actions as a result of 
sensations. For instance (see Fig. 94), nerve impulses come 
through the nerve of hearing to the auditory center, and we 
have hearing; this center is connected with the speech 
center ; and, as a result, we send out nerve currents to the 



204 



Physiology, 



organs of speech, and thus we speak in response to what 
we hear. Currents from the eye reaching the visual center 
may connect with the writing center, and we send out cur- 
rents by which we write in response to what we have read. 

Writing 



Speech 



Auditory 




Fig. 94. Connection of Brain Centers. (After Landois and Stirling.) 

Left Hemisphere Better Developed. — The " speech cen- 
ter " is in the left hemisphere; the right eye and ear, which 
connect with the left brain, are better developed than the 
left, and in general the left hemisphere seems superior (in 
right-handed persons) to the right. 

The Function of the Cerebellum. — The cerebellum is the 
center for regulating the actions of the skeletal muscles. 



The Brain. 205 

When we walk or run, or even stand still, a number of 
muscles must act, and act in concert. The nerve impulses 
originate in the cerebrum, but the cerebellum is the center 
for harmonizing the action of these various muscles. When 
the cerebellum is injured, an animal staggers instead of 
walking steadily. 

Functions of the Spinal Bulb. — The spinal bulb is the 
enlarged part of the spinal cord which is within the cra- 
nium. From it arise all the cranial nerves except the first 
five pairs. The spinal bulb is also the center for the con- 
trol of respiration, of circulation, of swallowing, and perhaps 
for many other processes. 

Brain Work and Brain Rest — Sleep is not merely rest 
for the body ; it should be complete rest for the brain. In 
so far as there are dreams, it would seem to indicate a par- 
tial activity ; that is, incomplete rest. The brain, like the 
muscles, needs exercise, and it also needs regular periods 
of rest. If a nerve cell is not kept active by the passage 
of nerve impulses through it, it usually dwindles away, 
and may entirely lose its power. 

Sleeplessness. — Intense brain work, without sufficient 
sleep, is likely to lead to sleeplessness, as when one has 
some subject of special study in hand and either will not 
or cannot throw it off. Perhaps inventors are as subject 
to this sort of trouble as any one class of men. Keeping 
the blood continually in the brain is likely to lead to a per- 
manent congestion, or inflammation, that may cause seri- 
ous, if not fatal, results. 

Fatigue. — It is stated that brain workers need more 
sleep than those who work chiefly with the muscles. Fa- 
tigue of the voluntary muscles is much more a matter of 



206 Physiology. 

nervous than of muscular origin. When one is completely 
"tired out," as he would say, if his mind can be aroused, 
as by some excitement, he will be found able to expend a 
good deal more muscular energy. So, too, many persons 
of slight muscular build, but of great " will power," are 
able to do more work with the muscles than others with 
larger muscles and less will. During fatigue the cell 
bodies are found to decrease in size, but there is no per- 
ceptible change in nerve fibers as a result of fatigue. 

Blood Supply of the Brain. — Blood is supplied to the 
brain through four arteries : the right and left internal 
carotid arteries, and the right and left vertebral arteries. 
These arteries are so connected by cross-branches that if 
any three of them should be compressed, or the blood 
flow in them otherwise stopped, the fourth would still be 
able to give the brain blood enough for its work. When 
the brain is more active it receives a larger supply of 
blood. During sleep it is paler. 

Cause of Fainting.— If the supply of blood to the brain 
is shut off, unconsciousness quickly follows. In the ordi- 
nary faint the blood supply to the brain has been reduced. 
It is due to checking the action of the heart from some 
emotion, or bad air, as in a close room ; severe pain may 
be the cause ; a blow over the pit of the stomach may stop 
the heart by reflex action. 

Apoplexy. — Apoplexy is caused by rupture of a blood 
tube and the formation of a clot that presses on the brain. 

Meningitis. — Meningitis is an inflammation of the mem- 
branes immediately surrounding the brain or spinal cord 
or both. 



The Brain. 207 

Summary. — 1. The outside of the brain consists of gray matter, the 
inside of white matter. 

2. The twelve pairs of cranial nerves are distributed to the head, with 
the exception of the tenth and part of the eleventh. 

3. The cranial nerves include the senses of sight, smell, taste, and 
hearing. 

4. Each hemisphere of the brain is connected with, and has chief 
control of, the opposite half of the body. 

5. The gray matter of the cerebrum is the seat of the will, sensation, 
thought, and emotion. 

6. The cerebellum regulates voluntary motion. 

7. Many of the cerebral functions have been located. 

8. The brain needs rest. In sleep less blood flows through the 
brain. 

9. Work reduces the size of nerve cells. During rest they increase 
again. 

Questions. — 1 . Is there any special reason why the " speech center " 
should be in the left cerebral hemisphere ? 

2. Why does a light lunch sometimes enable one to go to sleep after 
mental work ? 

3. Why is it uncomfortable to hold the head down ? 

4. How does the nervous system resemble a telegraph system ? In 
what respects are the two unlike ? 

5. Name some remedies for sleeplessness. 



CHAPTER XXII. 

THE SENSES. 

THE GENERAL SENSES. — TOUCH AND TEMPERATURE 

SENSE. 

Afferent and Efferent Nerve Currents. — Up to this point 
we have been studying efferent, or out-going, nerve cur- 
rents, such as control muscles and glands. Now let us 
turn to the in-coming, or afferent, currents ; for it is by- 
means of the afferent currents to the brain that we get all 
our sensations. In other words, it is through these cur- 
rents that we get all our knowledge. 

Two Classes of Sensations. — There are two classes of 
sensations, the special and the general. The special senses 
include sight, hearing, taste, smell, touch, and temperature 
sense. Among the general sensations are hunger, thirst, 
fatigue, nausea, satiety, f aintness, pain, muscular sense, etc. 

Special Sensation due to External Force. — Sensations 
from the organs of special sense are due to the action of 
an external force. For instance, sound waves entering the 
ear affect the nerves of hearing, and we have a sensation 
of hearing. Light acting on the optic nerve gives sight. 

General Sensations due to Conditions within the Body. 

— There are nerves of general sensibility in all parts of 
the body. The endings of these nerves are acted on by the 
blood and lymph. Currents are all the time coming through 

208 



The Senses. 209 

these nerves to the brain. But ordinarily we are not con- 
scious of them. If the body is in need of food, the mes- 
sages are stronger and we have a sensation of hunger. If 
the poisonous waste matters are not removed by the organs 
of excretion, their presence in the lymph is reported to the 
brain, and we have a feeling, perhaps of fatigue, or of 
decided discomfort, or even of pain. 

The Muscular Sense. — In judging the weight of a body 
by holding it in the hand, our estimate is the result of sen- 
sations aroused by nerve impulses from the organs used. 
There are afferent nerve fibers with endings in (1) the skin, 
(2) the muscles and tendons, and (3) the joints. In hold- 
ing out the arm and in moving it up and down, all three 
of these sets of nerve endings are stimulated, and impulses 
are conveyed to the brain producing the muscular sense. 

Dependence of Sight on Muscular Sense and Touch. — It is difficult to 
realize the importance of the muscular sense. An illustration of the as- 
sistance which touch and the muscular sense give to the sense of sight 
is furnished in the case of a boy who had been blind from birth, and re- 
ceived sight at the age of twelve years by means of a surgical operation. 
At first he could not distinguish a globe from a circular card of the same 
color until he had touched them. He knew the peculiar features of the 
dog and the cat by feeling, but not by sight. Happening one day to 
pick up the cat, he recognized for the first time the connection between 
the new sense of sight and the old familiar ones of touch and the mus- 
cular sense. On putting the cat down he said, " So, puss, I shall know 
you next time.*' 

Pain. — The nerves of general sensibility give informa- 
tion of the state of nutrition in the tissues and the condi- 
tion of the body as a whole. Ordinarily we are not aware 
of these nerve currents. When they become stronger 
than usual they give rise to feelings of general discomfort, 
such as fatigue, depression, restlessness, etc. When the 
currents become stronger still, we have pain. 



210 Physiology, 

Use of Pain. — Pain is a warning of over-use or injury. 
The milder nerve impulses that cause slight discomfort 
ought to be sufficient to call attention to the condition. But 
often these first reports are neglected. For instance, over- 
use or abuse of the eyes may cause irritation, that is allowed 
to go unheeded. The person may show the effect, by rub- 
bing the eye, but, being absorbed in study, may fail to 
stop reading and go on until there is actual pain. When 
the first warnings are not heeded, pain follows and demands 
attention. 

Pain in the Skin. — While the internal organs are ordina- 
rily without feeling, the skin is especially sensitive. The 
skin senses stand guard at the outposts of the body's 
camp, and give warning of approaching danger. No 
enemy may enter without being discovered by these keen 
sentinels, and the alarm is given. In amputating a limb 
the chief pain is in cutting through the skin. It is a com- 
fort to know that the more severe wounds do not cause 
pain in proportion to their extent 

Hunger and Thirst. — The cause of these sensations in 
a healthy body is plainly the need of food and water 
throughout the system. The sensation of thirst seems to 
be in the throat, and the longing may be somewhat re- 
lieved by merely moistening the throat. So hunger may, 
for the time, be appeased by filling the stomach with indi- 
gestible material. But the sensation soon returns. The 
system has a crying need, and it is not to be put off. 
That these sensations are really demands made by the 
body as a whole may be shown by the fact that they are 
permanently relieved by introducing food and water into 
the body (by the rectum, for instance), in which case the 
throat and stomach have nothing given them directly. 



The Senses. 



21 I 




Since, however, food and drink naturally enter by the 
throat and stomach, the mucous membrane of these 
organs has become the spokesman of the body. 

What we learn by touching Objects. — Let one person 
rest the hand flat on the table, palm upward, and close the 

eyes. An object placed on the 
palm, by another person, may give 
rise to various sensations, so that 
it may be described as rough or 
smooth, light or heavy, hot or 
cold, wet or dry, etc. If now the 
thumb and fingers are raised and 
applied to the object, more definite 
information will be gained as to its 
shape, size, surface, etc. Now 
raise the object in the hand, and 
further appreciation will be gained 
as to its weight. These experi- 
ments show that several sensations are involved in the 
handling of objects, and that the knowledge so gained is 
complex. 

Cutaneous Sensations. — The sensations from objects 
resting on the skin of the hand may all be referred to im- 
pressions made on nerve endings in the skin, and are 
called cutaneous sensations. They include: (i)the pres- 
sure sense, or touch proper, (2) the temperature sense, and 
(3) pain. 

Nerve Endings in the Skin. — The skin consists of two 
layers, the epidermis and the dermis (see Figs. 64 and 65). 
In the papillas of the dermis are nerve endings called 
touch corpuscles (see Fig. 95). 



Fig. 95. Papilla of Skin with 
Touch Corpuscle. 



212 Physiology, 

Pressure on the skin affects these nerve endings, and 
starts impulses that pass along the sensor fibers, through 
the spinal cord, to the brain, and give us sensations of 
touch. If a nerve fiber is touched, not at the end, but 
somewhere along its course, we get a sensation, not of 
touch, but of pain. 

The Sense of Touch. — Of the special senses the most 
general is that of touch. Seeing and hearing, taste and 
smell, belong to very limited parts of the outside of the 
body, but we have the power of feeling ail over the surface 
of the body. Except in the mouth and nose, we get. little, 
if any, sense of touch from any organ but the skin. The 
lining of the digestive tube and the internal organs gener- 
ally lack this sense. 

The Pressure Sense. — The sense of touch, proper, is 
strictly a presstwe sense. If we test the skin to find what 
regions are able to detect the least pressure, it is found 
that the forehead is most sensitive, and nearly equally so 
are the temples, back of the hand, and forearm. 

Location of Touch Sensations. — Each small spot of skin 
has its own nerve endings and each nerve fiber connects 
with a particular part of the gray matter of the brain. The 
brain can therefore tell where each nerve current came 
from, and thus we locate a sensation. 

Accuracy in locating Touch Sensations. — The accuracy 
varies, and is ordinarily keenest where the nerves are most 
numerous. Where the sense of locality seems to be im- 
proved by cultivation, this appears to be due to keener per- 
ception in the brain cells, and not to changes in the nerves 
or nerve endings. This is shown in the fact that if the 
fingers of one hand become more skilled in touch by prac- 



The Senses. 213 

tice, it will be found that the fingers of the other hand, 
without special training, are also improved. 

Test by Compass Points. — The delicacy of localizing 
touch is usually tested in this way. The blunted points of 
a light pair of compasses are allowed to rest gently on the 
skin of various parts of the body. If the two points are 
very close together, they will he felt as one pressure. That 
part which can best distinguish, as two points of touch, 
these blunt points, is considered the most sensitive. By 
this test the tip of the tongue is the most sensitive, being 
able to distinguish, as two separate points of contact, the 
tips of the compasses when only one twenty-fifth part of 
an inch apart. Following is the order of degrees of sensi- 
tiveness : tip of tongue, tips of fingers, lip, tip of nose, eye- 
lid, cheek, forehead, knee, neck ; while the middle of the 
back seems least sensitive. 

Reference of Sensation to the Region of Nerve Endings. — 
If the " funny bone," or " crazy bone," be hit, i.e. if the 
ulnar nerve be bruised against the bone, sharp pain may 
be felt in the wrist and hand, and soreness of these parts 
may be felt for days, though they are not in the least 
injured, but only the nerve at the elbow. The currents 
along this nerve rouse sensations that we have learned to 
locate at the endings of the nerve fibers. If, then, owing 
to injury, the currents start from the elbow, the brain still 
refers them to the nerve endings in the hand and wrist. 
So, too, after amputation of a hand or foot, there may 
for years be sensations referred to the missing member, 
probably due to irritation of the nerves of the stump. 

The Temperature Sense. — Many cases are on record in 
which, from accident or disease, the sense of touch was 
lost and the temperature sense retained, or vice versa. 



214 Physiology. 

Such facts have led to the belief that the temperature 
sense is distinct from that of touch, and has its own nerve 
fibers and nerve endings. 

Summary. — i . The special senses result from the action of external 
forces, such as light, heat, etc. 

2. General sensations are referred to our bodies and their condition. 

3. The muscular sense depends on impulses from muscles, tendons, 
and joints. 

4. The muscular sense and touch aid the sense of sight in giving us 
correct perceptions of size and form. 

5 . Pain is a general sensation. It is a warning — the cry of a senti- 
nel that an enemy has passed the picket line. 

6. Hunger and thirst indicate the need of food and drink. They 
are local signals of a general want. 

7. The cutaneous sensations are touch, temperature sense, and pain. 

8. There are touch corpuscles in the papillas of the dermis. 

9. Touch is the most general of the senses. 

10. Touch proper, or pressure sense, is tested by perception of pres- 
sure. 

11. Touch localization is tested by discrimination as to the distance 
of two points of contact. 

12. Temperature is discerned by a special set of nerve fibers. 

13. Sensations are referred to the region of the nerve endings. 

Questions. — 1 . What is the explanation of tickling. 

2. Where does the change occur by which we become more skilled 
in the sense of touch ? 

3. Why does an emotion, such as shame, make one feel hot ? 

4. If we had no sense of pain, what might result ? 

5. If we pass by a meal time without eating why does the sense of 
hunger usually disappear ? 



CHAPTER XXIII. 

THE SENSE OF SIGHT. 

Protection of the Eye. — The eye is set well back in its 
socket and guarded by three bony projections, — the brow, 
cheek bone, and the bridge of the nose. It is further 
protected by the eyelids and eyelashes. 

The Lacrymal Secretion. — The lacrymal gland, or tear 
gland, is just above the outer angle of the eye, and pours 
its secretion over the eyeball. The lids serve as curtains 
to admit or shut out light, and, by winking, wash the eye. 
It is as though a man were kept all the time in front of a 
plate-glass window, with water and rubber scraper, to keep 
it clean and bright. The lacrymal secretion is ordinarily 
carried off into the nasal cavity as fast as it is made. If 
the ducts are stopped, or if the secretion is formed very 
rapidly, the liquid overflows on the face as tears. 

The External Parts of the Eye. — The " white of the 
eye" is the sclerotic coat. It has blood tubes, but ordina- 
rily they are not conspicuous. The front part of the eye- 
ball is covered with the cornea. This is transparent, and 
the color of the iris shows through the cornea. In the 
center of the iris is the hole, or pupil, by which light enters 
the interior of the eye. 

The Conjunctiva. — The front of the eyeball is covered 
by a thin, transparent, mucous membrane, the conjunctiva, 
which turns back and lines the inside of the eyelids. It is 
very sensitive. 

215 



2l6 



Physiology. 



Movements of the Eye. — There are six pairs of muscles which move 
the eyes to right and left, up and down, and give rotary movements. 
The two eyes move in the same direction at the same time, though in 
looking at near objects the two eyes both point inward, so that one 
appears cross-eyed. 

Dissection of an Eye. — The muscles and external parts of the eye 
may readily be seen by examining the eye of a rabbit in its natural 
position and then dissecting it out. A beef eye should be obtained 
from the butcher and the structure of the eye learned by following the 
description. 

Ciliary Muscle 




Muscle of 
Eyeball 



Optic Nerve Choroid 

Fig. 96. Horizontal Section of Right Eye. 

The Coats of the Eye. — There are three coats, the outer 
or sclerotic, the middle or choroid, and the inner or retina. 

The Sclerotic Coat. — This is of a dull white color, con- 
stituting the " white of the eye." It is thick and tough, 
holding all the contained parts firmly and furnishing suffi- 
cient strength for the attachment of the muscles that move 
the eyeball. 



The Sense of Sight. 217 

The Choroid Coat. — The middle coat of the eye is the 
choroid- It is thinner than the sclerotic and of much more 
delicate structure. It is full of blood tubes, and has an 
inner lining of dark color to prevent the reflection of light 
in the eye, just as most optical instruments are painted 
black on the inside. 

The Retina. — The retina is an expanded part of the 
optic nerve and forms an inner coat that lines all but the 
front part of the eye. It is a thin, translucent film, some- 
what like the film that forms over the white of an egg when 
it is first dropped into hot water. It is very delicate and 
easily torn. The retina is the only part of the eye that is 
sensitive to light, and on it the images must be formed to 
produce distinct vision. 

The Cornea. — The clear front part of the eye is the 
cornea. It is a continuation of the sclerotic coat and is 
more bulging than the rest of the front of the eye, as can 
be seen by taking a side view of the eye, or by noticing 
some one who closes the eyelids and rolls the eyes about. 

The Iris. — This is the part that gives the color to the 
eye, or if the pigment that gives the color is lacking, the 
blood gives the pink color seen in albinos. The iris is a 
forward continuation of the choroid coat. 

The Pupil. — Most of the light that passes through the 
transparent cornea is stopped by the opaque iris. But in 
the center of the iris is a round hole through which light 
enters the interior of the eye. The pupil looks dark be- 
cause it is the only opening into a dark room. 

Regulation of the Amount of Light admitted into the Eye. — 
Hold a hand glass between the face and a well-lighted window. Note 
the size of the pupils. Quickly turn toward the darkest part of the 
15— PHY ~ 



2 1 8 Physiology. 

room. The iris has circular muscle fibers that make the pupil smaller 
when there is too much light for the eye, and when the light is feeble 
the pupil opens wider. 

The Aqueous Humor. — There is a small space between 
the cornea and the iris. In this space is the clear, watery 
aqueous humor. 

The Vitreous Humor. — All but the front part of th~ 
space within the eye is filled with a clear, jelly-like sub 
stance, the vitreous humor. 




Fig. 97. The Formation of an Image on the Retina. 

The Crystalline Lens. — Just back of the iris is a double- 
convex lens, clear as crystal, and of about the consistency 
of a gumdrop. It is less convex on the front surface. 

Experiment with Lens to show Inversion of Image. — Take a 
double-convex lens or any hand magnifier. Hold this up at the rear 
of the room and catch the inverted image of the window on a piece of 
paper held back of the lens. This illustrates how the image of an 
external object is formed by the crystalline lens upon the retina of 
the eye. 

Experiments to illustrate the Adjustment for Distance. — (i) Stick 
a pin at each end of a book cover. Hold the book at about the usual 
distance for reading, so that the two pins are in a line with the eye. 
Look closely at the nearer pin, and the second pin will appear indistinct 
and double. Now look closely at the head of the farther pin. The 
nearer one may be seen doubled, but not sharply. (2) Hold the tip of 
a pencil in a line with any object, say a picture, on a wall opposite. In 
looking at the tip of the pencil the picture is dim. Now look by the pen- 
cil at the picture, and the point of the pencil will be blurred and doubled. 

Accommodation. — We cannot, at the same time, see 
distinctly a near and a distant object. When we look at 



The Sense of Sight. 



219 



a near object the lens becomes thicker, and when we look 
at a distant object the lens becomes less thick. This ad- 
justment is called accommodation. 



CILIARY MUSCLE 




FAR NEAR CILIARY PROCESS 

Fig. 98. Changes of the Lens in Accommodation. 

The Blind Spot. — Light falling on the optic nerve itself has no effect 
in giving a sensation of light. If the light falls on the spot where the 
optic nerve enters the eyeball, we see nothing. Hence, this spot is 
called the blind spot. 

Experiment illustrating the Blind Spot. — At the left (as looked at 
by the class) of a long blackboard make a bright circular spot, three 
inches in diameter, with white or yellow crayon. Beginning at the 
right of this write the figures 1, 2, 3, etc., along the whole length of the 
board, about eight inches apart. Let each pupil close the right eye and 
look at the bright spot. Then let each read the figures, passing slowly 
from one to another, at the same time noticing whether the bright 
spot can be seen. To succeed in this the eye must not be allowed to 
waver. Have the pupils tell when the bright spot disappears, then 
read on, and note when the spot reappears. 

Another Experiment. — In this experiment shut the right eye, and 
be careful not to let the eye waver. 

>fc Read this line slowly. Can you see the star all the time? If the 
star does not disappear before reaching the end of the line, let the eye 
travel on to the right of the page, or hold the book nearer the face. 
In the human eye the optic nerve enters the eye not in the center, but 
nearer the nose, so that in turning the left eye toward the right at the 
proper angle, the image of the star falls upon the spot where the optic 
nerve enters. As this spot is insensitive to light, the star no longer 
appears. 



220 



Physiology. 



The Structure of the Retina. — The retina is very complicated in its 

structure. No less than ten layers have been distinguished, as shown 
in Fig. 99. The rays of light pass through the retina, and produce 
their effect on the rods and cones which constitute the outer (back) 
layer ; and the nerve impulses aroused by the light must return through 
the thickness of the retina to be conveyed along the nerve fibers of the 
innermost layer of the retina to the optic nerve. 



nner or Vitreous Surface 




Internal Limiting Layer 
Layer of Nerve Fibers 
Layer of Nerve Cells 



Inner Molecular Layer 

Inner Nuc'ear Layer 

Outer Molecular Layer 

Outer Nuclear Layer 
External Limiting Layer 
Layer of Rods and Cones 
Layer of Pigment Cells 



Outer or Choroid Surface 
Fig. 99. Section of the Retina. (Waller.) 

Importance of the Retina. — The chief structure in the 
eye is the retina. Without this all else is useless. If light 
falls on the retina, nerve impulses pass along the fibers of 
the optic nerve to the brain, and we have a sensation of 
light. But in order to see anything distinctly, the light 
must fall on the retina in such a way as to form a distinct 
image of that object. If the lens be removed, or becomes 
opaque, as in " cataract,'' we see objects very indistinctly, 
though we may be able to tell light from darkness. Light 



The Sense of Sight. 221 

from an object passes through the cornea, aqueous humor, 
lens, and vitreous humor, and the rays are so refracted as 
to form an inverted image on the retina. 

The Optic Nerve not Sensitive. — The optic nerve, while capable 
of carrying nerve impulses that cause sensations of light, is not itself 
sensitive to light. If the optic nerve be cut, it does not give pain, but 
gives the sensation of a flash of light. 

Sympathy between the Two Eyes. — While most of the 
fibers from each optic nerve cross to the other side of the 
brain, some fibers go to the same side of the brain. We 
can therefore better understand the close sympathy be- 
tween the two eyes. 

Color Blindness. — It is found that some persons cannot distinguish 
certain colors. Blindness to red and green are most common. This 
is a matter of importance among railroad men and sailors, where it is 
necessary to distinguish red and green signals. 

Summary. — i. The eye is protected by its bony surroundings, lids, 
lashes, tears, sensitiveness of the conjunctiva, etc. 

2. The eye has three coats — sclerotic, choroid, and retina. 

3. The pupil is a hole in the iris, and varies in size to regulate the 
amount of light admitted. 

4. The cornea, aqueous humor, lens, and vitreous humor form an 
inverted image on the retina. The eye is a camera, darkened inside. 

5. The lens changes its thickness for seeing at different distances. 

6. Suitable glasses overcome many of the defects in eyesight. 

7. The retina is an expansion of the optic nerve, and is exceedingly 
complicated in its structure. 

8. The blind spot is the place where the optic nerve enters the eye. 

9. The optic nerve is insensitive to light, but injury to it causes sen- 
sations of light. 

10. Most of the fibers of the optic nerve cross to the other half of 
the brain, but some do not cross. 

1 1 . Defects in eyesight are much more common among civilized men 
than with the uncivilized. 



222 Physiology. 

12. The care of the eyes must be made a subject of study and care- 
ful thought by all reading people. 

Questions. — i . What is " cataract " ? 

2. What is the cause of " double vision " ? 

3. Why does the well eye sympathize with the affected one? 

4. Why does looking at a bright light often cause a person to 
sneeze? 

5. What is the condition of one who is " cross-eyed " ? 

6. Compare the pupils of a man, a cat, and a cow. 

7. Does the color of the eye have any relation to the strength of 
eyesight ? 

8. Why is one blinded on entering a bright room from the dark? 

9. Why is one going from a bright room into the dark unable to 
see at first, but gradually sees more distinctly? 

10. Why can one not see well when the eye " waters " ? 

1 1. Should the lights which illumine a pulpit or platform be so placed 
that they can shine into the eyes of the congregation? How should 
they be arranged? 

12. If each eye has a blind spot, why are there not blank spaces in 
the field of vision ? 

13. What advantage has a stereoscopic view over a single view? 
How are stereoscopic views made? 



CHAPTER XXIV. 
DEFECTS OF EYESIGHT AND CARE OF THE EYES. 

DEFECTS OF EYESIGHT. 

The Wearing of Glasses. — It will be noticed that many 
people, even children, nowadays wear spectacles or eye- 
glasses. The reason for this is probably not entirely 
because people's eyes are more defective now than they 
were fifty years ago ; but partly because everybody, chil- 
dren and all, now have to use their eyes a great deal more 
than people did fifty years ago. Evidence of certain defects 
of the eyes for which glasses are worn show themselves 
more now than they did then; and therefore glasses have 
to be worn more. 

Symptoms of Defective Eyes, — Many children suffer 
from headaches, or their eyes are red and watery. Some- 
times they cannot plainly see the writing or drawing on 
the blackboards, or they appear to be stupid, or hold their 
books close to their eyes when reading or studying. Such 
children probably have some defect of the eyes which 
glasses will remedy. They should be sent to the oculist 
to have their eyes examined, and if it be found that they 
need glasses, they should wear them. It does not always 
follow that a person does not need glasses because he can 
see well ; defects in his eyes may require such great effort 
of the eye muscles that control the focusing of the eyes as 
to cause headaches, nervousness, and other troubles which 
a properly fitting pair of glasses will remedy. 

The Focus. — If an object is to be seen clearly, the eye, 

223 



224 Physiology. 

like a photographic camera, has to be focused for the par- 
ticular distance at which the object is placed. In the 
photographic camera the " focusing" is done by moving 
the lens nearer to or farther from the plate or film, accord- 
ing as the object to be photographed is farther from or 
nearer to the camera. To get a clear picture in pho- 
tography, therefore, the length of the camera must be 
adjusted to the distance from the camera of the object to 
be " taken." When the object is a short distance from 
the camera, the " bellows " is pulled out and the camera is 
lengthened; when the object is farther away, the " bellows " 
is pushed in and the camera is shortened. If the camera 
is not properly " focused," a clear photograph cannot be 
taken. So also if one's eyes be not properly " focused," he 
cannot see clearly. 

The Crystalline Lens. — The eye is '/focused" in a dif- 
ferent way. It cannot be made longer when we look at 
nearby things, or shortened when we look at more dis- 
tant objects. Instead of this, the eye is "focused" by 
changing the shape of the " crystalline lens," which lies 
just back of the iris and the pupil, and which performs in 
the eye the same service that the glass lens does in the 
photographic camera; viz., it throws upon the retina, just 
as the camera lens does upon the photographic plate or 
film, an image of the object at which we are looking. Now, 
if we could change the thickness of the glass lens in the 
camera, making it thicker when photographing near objects 
and thinner when photographing those farther away, we 
should be doing in the camera just what is done in the eye 
when we " focus " it. In the eye, when we look at a nearby 
object, the crystalline lens becomes thicker ; when we look 
at a more distant object, the crystalline lens becomes thin- 



The Sense of Sight. 225 

ner or flatter. It is made thinner and flatter by being 
pressed upon by elastic connective tissues between which 
it lies, just as a soft rubber ball will be made flatter if it be 
put between two layers of a handkerchief and the sides of 
the handkerchief pulled upon. 

The Natural Focus. — In a state of nature the eye is 
used mostly for looking at distant objects, and not for 
looking at books and near objects, as we now have to do 
many hours at a time. Nature made the eye so that it 
would be focused for the distance by the elastic pull of the 
coats of the eyeball. Elastic coats not being made to work 
by nervous energy, as muscles are, never grow tired, as 
muscles do when they work. Nature made our eyes so 
that they would be focused for distant objects without any 
muscular action. Therefore, our eyes do not tire when 
we look at the distance ; they are " resting." But in order 
that we may also clearly see near objects, our eyes are so 
made that the crystalline lens may be made thicker. Since 
in a state of nature the eyes are not used very often nor 
for very long periods in looking at near objects, the focus- 
ing for near objects is done by muscular action. Hence, 
the eyes become tired when they are used for long periods 
in looking at near objects. 

" Accommodation." — Everybody has seen a lady's arm 
bag which closes by pulling the " puckering string." If 
the mouth of the bag were elastic, so that it would open 
itself if the string were not pulled, and if the string were 
a muscle, it would be something like the arrangement of 
elastic coats and muscles by means of which the eye is 
focused. Just behind the iris, where it is attached to the 
sclerotic coat of the eyeball, there is a very small circular 
muscle called the " ciliary muscle " or " muscle of accom- 



226 Physiology. 

modation." When it contracts, this muscle overcomes the 
pull of the elastic tissues, which causes the flattening of the 
crystalline lens, which, being elastic, becomes thicker, and 
the eye is focused for a near object. 

Effect of Age. — As people grow older, the crystalline 
lens, like the other parts of the body, slowly loses its 
elasticity. Hence when the pressure is relaxed by the 
action of the muscle of accommodation, the lens cannot 
become thick enough to focus the eye for very near 
objects. For this reason middle-aged people cannot clearly 
see objects as near to the eyes as young people can. This 
is called " presbyopia," from two Greek words meaning 
"old-eye." 

In order to see near things clearly, to read, etc., middle- 
aged people are compelled either to hold things off at 
arm's length, which is very inconvenient, or to put on 
glasses. But through these glasses they cannot see well 
at the distance, because the focus of the glasses is for a 
close object and cannot be changed. 




(2) Far-sighted Eye. (I) Normal Eye. (3) Near-sighted Eye. 

Fig. 100.* Defects in Eyesight. 

Far Sight. — It not infrequently happens that the eye- 
ball is not long enough from the front to the back to 
permit of proper focusing for objects at a great distance 
without bringing into use the muscle of accommodation. 
In other words, a perfect eye is focused for great distances 
when the muscle of accommodation is at rest. In the 



The Sense of Sight. 227 

short eye, however, clear vision cannot be had at any dis- 
tance, unless the muscle of accommodation be actively at 
work. Such eyes are called " far-sighted," or " hyper- 
metropic," from three Greek words meaning " over-meas- 
ured-eye," 

On account of the fact that such an eye cannot see 
clearly at any distance without calling into constant action 
the muscle of accommodation, that muscle has no periods 
of rest except during sleep. It is apt to tire out, therefore, 
and the person who has such eyes may be subject to 
headaches or other nervous troubles. To overcome this 
he should wear glasses. Although his glasses are the 
same kind that " old-sighted " people wear, the " far- 
sighted " person can see clearly at the distance as well 
as near by with his glasses, while the " old-sighted " person 
can see clearly only close objects with his. 

It not infrequently happens that the " far-sighted " per- 
son can see equally well at the distance with or without 
his glasses. But this is not a sign that he does not need 
glasses; on the contrary, it is a sign that he does need 
them ; for if he did not need them, he could not see clearly 
with them. 

If the eyes be too long from front to back, they cannot 
see clearly at a distance, but can see near objects clearly. 
Such eyes are called " near-sighted," or "myopic," from 
two Greek words meaning " mouse-eye," because near- 
sighted eyes, like the eyes of a mouse, are not infrequently 
quite prominent. 

The eyes of most babies are "far-sighted," but as the 
rest of their bodies grow, their eyes also generally grow 
until they become only slightly "far-sighted." Sometimes 
the growth of the eyes does not keep pace with the rest of 
the body and the eyes remain quite far-sighted; in other 



228 Physiology. 

cases they grow too rapidly in one direction, from the front 
to the back, and become near-sighted. Children with either 
far-sighted or near-sighted eyes should wear glasses, — the 
far-sighted to avoid headaches and nervous troubles, the 
near-sighted to enable them to see plainly at a distance. 

Near Sight. — When a child's eyes begin to grow near- 
sighted, there is danger that the near-sightedness will 
increase if special care is not taken to prevent it. The 
tissues of the child's eyes are comparatively soft and yield- 
ing. Children nowadays use their eyes a great deal for 
near work. The nearer any object is held to the eyes, the 
more the little muscles of accommodation pull upon the soft 
and yielding coats of the eyeball and tend to stretch them. 
Not only that, but the nearer any object is held to the eyes, 
the more the eyeballs turn inward; and the more they turn 
inward, the more they are pressed upon and squeezed by 
the six little muscles which move each eyeball. Thus pulled 
at from within and pressed upon from without, it not infre- 
quently happens that children's eyes become too long from 
before backward, that is, " near-sighted/' 

Children can clearly see objects which they hold very 
near to the eyes, and for this reason frequently get into the 
habit of doing so. This is a very bad habit indeed, for it 
tends to make the eyes near-sighted, or, since it tires the 
muscles which turn the eyeballs inward and the muscles of 
accommodation, not infrequently causes headaches. This 
habit should be carefully and constantly corrected, and no 
child should be allowed to hold objects nearer than about 
fifteen inches from the eyes. If it cannot see plainly the 
smallest print at that distance, something is wrong with 
the eyes. 

But the necessity for the wearing of glasses is not the 



The Sense of Sight. 229 

worst thing about near-sighted eyes. The tendency of 
near-sighted eyes is to grow more and more near-sighted 
unless great care is taken to prevent it. Even that, how- 
ever, would not be very bad, for it would require only the 
wearing of stronger and still stronger glasses. But as 
the eyeball becomes more near-sighted, it becomes longer ; 
and as it becomes longer, the membranes of which it is 
composed, especially the retina and the choroid coat, 
become more and more stretched and pulled upon, until 
they may even become diseased or pull apart, so that 
serious eye trouble, even blindness, may result from un- 
cared-for near-sightedness. 

Near-sightedness may, therefore, become a disease of 
the eyes. In fact, a near-sighted eye may be looked upon 
as a diseased eye. As near-sightedness occurs practically 
only among civilized people, it may be called a disease of 
civilization, and one would naturally expect to find it most 
prevalent among those people who use their eyes most for 
near work. Such is the fact. The Germans, of all people, 
use their eyes most for near work, and among them near- 
sightedness is very common. Another defect of the eyes 
occurs when the clear front parts of the eye (cornea and 
lens) are unequally curved so that the rays of light do not 
converge properly in the eye, the image on the retina is 
blurred, and the person thus afflicted cannot see clearly. 
This defect in vision, which is called astigmatism, can be 
corrected by specially prepared glasses. 

Importance of Proper Glasses. — It will thus be seen that 
glasses are very frequently a necessity for children. Nerv- 
ous, suffering, peevish, backward children, unable to keep 
up in their studies, are often changed into sturdy, happy, 
bright pupils who keep pace with their classes, simply by 



230 Physiology. 

fitting them with proper glasses. But as the proper fitting 
of glasses is not a simple thing, the child should be taken 
to an oculist, and glasses should not be purchased of ped- 
dlers. Ill-fitting glasses may be worse than none at all. 

THE CARE OF THE EYES. 

1. Objectionable Light. — In reading we wish light from 
the printed page. Hence we should avoid light entering 
the eye from any other source at this time. While reading, 
then, do not face a window, another light, a mirror, or white 
wall. White walls are likely to injure the eyes. Choose 
a dark cover for a reading table. Sewing with a white 
apron on has injured the eyes. Direct sunshine very near 
the book or table is likely to do harm. 

2. Position in Reference to Light. — Preferably have the 
light from behind and above. Sitting under and a little 
forward of a hanging lamp will allow the light to fall on 
the book and keep it away from the face. In reading by 
daylight avoid cross-lights so far as possible. 

3. Electric Light. — The incandescent electric- light has 
advantages in throwing the light downward and in giving 
out little heat ; but owing to its irregular illumination (due 
to the shadow cast by the wire or filament), it is not well 
suited for study or other near work. For this purpose an 
Argand gas or kerosene burner is much to be preferred, 
since it throws a soft, uniform, and agreeable light upon 
the work. 

4. Reading Outdoors. — Reading out of doors is likely to 
injure the eyes, especially when lying down. To read 
while lying in a hammock is bad. Too much light directly 
enters the eye, and too little falls upon the printed page. 



The Sense of Sight. 23! 

5. Reading Heavy Books. — Do not hold the book or 
work nearer the eyes than is necessary. So far as possible 
avoid continuous reading in large or heavy books by arti- 
ficial light. Such books being hard to hold, the elbows 
gradually settle down against the sides of the body, and 
thus the book is held too close to the eyes, or at a bad 
angle, or the body assumes a bad position. 

6. Resting the Eyes. — Frequently rest the eyes by 
looking up and away from the work, especially at some 
distant object. One may rest the eyes while thinking over 
each page or paragraph, and thus really gain time instead 
of losing it. 

7. Strength of Light. — Have light that is strong enough. 
At twice the distance from a lamp the light is only one 
fourth as strong. Reading just before sunset is not wise. 
One is often tempted to go on, not noticing the gradual 
fading of the light. 

8. Evening Reading. — Do the most difficult reading by 
daylight, and save the better print and the books that are 
easier to hold for work by artificial light. Writing is usu- 
ally much more trying to the eyes than reading. By care- 
fully planning his work one may economize eyesight. 
Weak eyes, by proper care, may outlast and do more work 
than those naturally stronger, but injured by abuse. Read- 
ing before breakfast by artificial light is usually bad. 

9. Reading during Convalescence. — Many eyes are 
ruined during convalescence. At this time the whole sys- 
tem is weak — including the eyes. There is a strong 
temptation to read, perhaps to while away the time, per- 
haps to make up for lost time in school work. This is a 
time when a friend may show his friendship. 



232 Physiology. 

10. Irritation of the Eyes. — If one finds himself rubbing 
his eyes, it is a sign that they are irritated. Stop read- 
ing, find the cause, and do not read on unless the irritation 
ceases. If any foreign object, as a cinder, lodges in the 
eye, it is better not to rub the eye, but to draw the lid 
away from the eyeball and wink repeatedly ; the increased 
flow of tears may dissolve and wash the matter out. If it 
be a sharp-cornered cinder, rubbing may merely serve to 
fix it more firmly in the conjunctiva. If it does not soon 
come out, the lid may be rolled up over a pencil, taking 
hold of the lashes or the edge of the lid. The point of a 
blunt lead pencil is a convenient and safe instrument with 
which to remove the particle. 

11. Keep the Eyes Clean. — Be careful to keep the eyes 
clean. Do not rub the eyes with the fingers. Aside from 
consideration of rules of etiquette, there is danger of intro- 
ducing foreign matter that may be very harmful. It is 
very desirable that each person have his individual face 

'towel. By not observing this rule certain contagious 
diseases of the eyes often spread rapidly. 



CHAPTER XXV. 

TASTE, SMELL, HEARING, AND THE VOICE. 

Uses of the Sense of Taste. — The sense of taste helps 
us in judging of the fitness of food. By reflex action the 
taste of agreeable substances aids in digestion by stimulat- 
ing the glands, especially the salivary glands. 

The Papillas. — The surface of the tongue is covered 
with papillas. Most of them are slender, and like the 

Papillas 



Glossopharyngeal 
Nerve (9th) 




Gustatory Branch of Fifth Nerve 
Fig. 101. Nerves and Papillas of the Tongue. 

papillas of the skin, are organs of touch. Scattered among 
these are larger papillas in which are the endings of the 
nerves of taste. 

The Nerve Supply of the Tongue. — The nerves of taste 
are the glossopharyngeal, distributed to the back part of 
the tongue, and the gustatory in the front part. The tip 
of the tongue seems to be most sensitive to sweets and 
salts, the back part to bitters, and the sides to acids. 
1 6 — phy 2 33 



234 



Physiology. 



Solution Necessary for Tasting — Substances must be 
dissolved before they can be tasted. If the tongue be 
wiped dry, and a few grains of salt or sugar be placed on 
it, the taste will not be perceived for a little time. Insol- 
uble substances give no taste. 

Flavors. — What we call flavors affect us more through the sense of 
smell than through taste. If the nose be held shut, a piece of onion 
placed on the tongue does not produce what we usually call the taste 
of the onion. By holding the nose we may get rid of the disagreeable 
part of taking certain medicines. Let the pupil experiment with various 
substances as above indicated. 

The Sense of Smell. — The nerves of smell, the olfactory 
nerves, are distributed in the walls of the nasal passages. 
The sense of 
odor gives us 
information as 
to the quality 
of food and 
drink, and more 
especially as to 
the quality of 
the air we breathe. Hence 
we find the organ placed 
at the opening of the 
respiratory passages, and 
close to the organ of 
taste. 



Olfactory Bulb 



Olfactory Nerves 

Branches of 
Fifth Nerve 



Turbinated Bones :: ; 




Fig. 102. Nerves of the Outer Wall of the 
Nasal Cavity. 



Why we Sniff. — In quiet breathing the air passes along the lower 
air passages just above the hard palate, When we wish to test the 
quality of the air, we sniff, that is, make a sudden inspiration by jerking 
the diaphragm down, and air from the outside then rushes into the 
upper nasal passages, over the walls of which the olfactory nerves are 
spread in the mucous membrane. In inflammation, as from a cold, 
the narrow nasal passages, especially the upper, are often closed. 



Taste, Smell, Hearing, and the Voice. 235 

The Parts of the Ear. — The parts of the ear are the 
external, the middle, and the internal ear. 

The External Ear. — The external ear gathers the sound 
waves, and directs them into the opening of the ear, but 
the loss of the external ear does not seriously interfere 
with hearing. The passage leading inward from the ear 
extends about an inch, and is then completely shut off 



Semicircular Canals 



Stirrup Anvil 




EUSTACHIAN^ ^ 



PHARYNX 



Fig. 103. Structure of the Ear. 



from the cavities beyond by a thin membranous partition, 
the tympanic membrane or drum skin. This passageway 
is guarded by hairs, and is further protected by wax 
secreted by glands of the lining. 

The Middle Ear. — Beyond the membrane of the tym- 
panum is a cavity called the middle ear. Extending across 
the cavity of the middle ear is a chain of very small bones, 
the hammer, anvil, and stirrup, the hammer being attached 
to the inner surface of the membrane of the tympanum, 



236 Physiology. 

and the stirrup being fastened by its base to the wall of 
the internal ear. 

The Eustachian Tube. — The middle ear communicates 
with the pharynx by means of a narrow tube called the 
eustachian tube. It admits air to equalize the pressure on 
the two sides of the tympanic membrane. This tube is 
closed most of the time, but opens when we swallow. 

The Internal Ear. — The internal ear consists of several 
complicated cavities and tubes which contain a liquid in 
which rest the nerves. The principal cavity is the cochlea, 
or snail-shell cavity, in which the nerve endings are con- 
nected with an exceedingly complicated apparatus. 

The Production of Sound. — Sound waves set the drum 
skin or membrane of the tympanum in vibration; the 
vibrations are conveyed by the chain of bones across the 
middle ear to the liquid of the inner ear. Through the 
complicated apparatus of the snail shell the vibrations of 
the liquid are made to start nerve impulses in the fibers of 
the auditory nerve, and when these nerve impulses are 
rightly received and interpreted by the brain, we have a 
sensation called sound. 

The Equilibrium Sense. — Probably most of the senses contribute 
to the maintaining of the equilibrium of the body by giving information 
as to position, motion, etc., especially sight and the muscular sense. 

Only that part of the auditory nerve which is distributed in the " snail 
shell " of the ear is now supposed to have to do with hearing. There 
seems to be good evidence that the semicircular canals inform us as 
to changes of the position of the body, and they are regarded as the 
seat of an " equilibrium sense." 

The Care of the Ear. — In cleaning the ear no hard sub- 
stance should be used ; even the finger nail is likely to 
do harm. A moistened cloth should be used. It is not 



Taste, Smell, Hearing, and the Voice. 237 

well to stuff the ears with cotton. If there is any trouble 
with the hearing, of course a physician should be consulted 
without delay. 

Colds and Deafness. — A cold often produces inflamma- 
tion of the mucous membrane of the pharynx. This in- 
flammation may extend along the eustachian tube to the 
middle ear and affect the hearing. See " Adenoids," p. 95. 




Epiglottis 
Base of Tongue 

Hyoid Bone . 



False Vocal Cord 
Ventricle 
Vocal Cord 



Cartilage 



..Trachea _ 

FROM RIGHT TO LEFT MEDIAN 

Fig. 104. Longitudinal Sections of the Larynx. 




The Ear and the Voice. — The delicate structure of the 
ear is fully matched by the fine adjustment and range of 
the voice. The voice is produced in the larynx at the upper 
end of the windpipe. The projecting angle of the larynx 
is called " Adam's apple. " 

The Vocal Cords. — The vocal cords are not cord-like. 
They are mere ridges projecting inward from the sides of 
the larynx. They maybe stretched to various degrees and 
placed in different positions, according to the sound that 
is to be produced. 




238 Physiology. 

The Position of the Vocal Cords. — While we are quietly 
breathing, the vocal cords lie back, like low ridges, against 
the sides of the larynx, and offer nearly the whole channel 
of the larynx for the free passage of air for breathing pur- 
poses. But when we wish to produce vocal sound, the 
vocal cords are made to stand out farther from the side 
walls, and interfere with the free passage of the air. The 
vocal cords are attached close to each other in front, but 
at the back of the larynx they diverge widely, forming a 



SC[___ Epiglottis ^S. 

L. — False Vocal Cords 

— . ^. True Vocal Cords 



Glottis Narrowed, High Note Glottis Wider, Quiet Breathing 

Fig. 105. The Vocal Cords, seen from Above 

letter V, with the angle of the V just back of Adam's 
apple. "When changes in the voice or in breathing are 
being made, the white glistening vocal cords may be seen 
to come together or to go apart like the blades of a pair of 
scissors.'' In a high note the cords are close together and 
nearly parallel. As the air is forced past the edges of the 
vocal cords, they are set in vibration, and produce the 
sound called the voice. 

Illustration of the Vocal Cords. — The principle of the action of the 
vocal cords can be illustrated by the common toy known as the squeak- 
ing balloon, or "squawker." Here the air is driven out past a band of 
rubber stretched across the inner end of the tube. If instead of one 
band with both edges free, we were to tie on the inner end of the tube 
two bands of rubber, each covering the outer edge of the tube, leaving 
the inner edge of the rubber free, and with the two bands touching at 
one end and considerably separated at the other end, we would have a 
pretty fair resemblance to the larynx. 



Taste, Smell, Hearing, and the Voice. 239 

Loudness of Voice. — The loudness of the voice depends on the force 
with which the air is driven past the cords, and on the size and con- 
dition of the cords themselves. 

Pitch of Voice. — Pitch depends on the rapidity of the vibrations, 
which is determined by the length of the cords and their tension. 
Other things being equal, the size of the larynx would determine the pitch. 

Voice and Speech. — The larynx by itself produces vocal sound 
merely. In speech the sounds produced in the larynx are much modi- 
fied by the lips, tongue, teeth,, cheeks, etc. We have voice as soon as 
born, but we only gradually acquire the power of speech. This dis- 
tinguishes man from the animals below him. 

Summary. — i . Taste enables us to judge of the quality of food, and 
it indirectly influences digestion. 

2. The tongue has two nerves of taste, the fifth pair of cranial nerves 
supplying the front, and the ninth pair the base. 

3. So-called flavors affect the sense of smell more than that of taste. 

4. The sense of smell tests food and air. 

5. Agreeable odors promote respiration. 

6. The ear consists of the outer, middle, and inner ear. In the 
inner ear are the endings of the auditory nerve. 

7. The semicircular canals have to do with the sense of equilibrium 
and not with hearing. 

8. Colds and catarrh often seriously affect hearing. 

9. The larynx is very complicated. Various muscles move the car- 
tilages and vary the length and tension of the vocal cords, and thus 
produce the varying degrees of pitch. 

10. The vocal cords are not cords, but are band-like ridges on the 
sides of the larynx. 

11. The higher animals have voice but not speech. 

12. Whispering is speech without voice. 

13. The larynx is affected by " colds " and catarrh. 

Questions. — i . How may the sense of taste be blunted ? 

2. What is the effect of inhaling menthol ? 

3. Does a person w r ho is deaf in one ear hear " half as well " as before ? 

4. Which of the senses goes to sleep first when we go to bed ? 

5. In what order do the other senses go to sleep ? 

6. In what order do the senses waken in the morning ? 

7. Why does one become hoarse from hearing others shouting ? 



CHAPTER XXVI. 

ACCIDENTS. — WHAT TO DO TILL THE DOCTOR COMES. 

How to Stop Flow of Blood from Arteries. — In case of bleeding 
from an artery the blood comes in jets. Pressure should be applied 
between the cut and the heart. To know where to apply the pressure, 
study the course of the main arteries. By examining Fig. 32 it will be 
seen that the arteries to the arms pass down the inside of the upper 
arm. Here they come near the surface. By putting a thick book or 
roll under the armpit and pressing the arm down firmly, the artery may 
be compressed. 

Bleeding from the Upper Arm. — In case of a deep cut in the lower 
part of the arm, a handkerchief should have a knot tied in it, and the 
knot placed over the artery ; that is, on the inside of the arm just below 
the armpit. Pass the handkerchief around the arm and tie it loosely. 
Then run a stick through it, and twist till the knot is drawn tightly 
against the artery. Instead of a knot, a potato, or anything else to 
make a firm lump, may be used. (See Fig. 32.) 

Bleeding from the Neck. — In studying the pulse, we found the 
carotid artery in the neck. If a deep cut has been made in the upper 
part of the neck, it may be possible to stop the flow by compressing 
the artery lower down the neck. 

Wounds in the Thigh, — The femoral artery comes near the surface 
in the groin. Pressure may be applied here in the same way to stop 
bleeding from a cut farther down the thigh. In the angle back of the 
knee, pressure may compress the artery supplying the leg. In case of 
severe wounds, pressure should be applied immediately to the wound. 
Sometimes it is well to make a plug of cloth and press upon the cut. 

Bleeding from Veins. — In case of bleeding from veins, holding the 
part up may check the flow. If necessary to apply pressure, it should 
be beyond the cut, instead of between it and the heart, as in the case of 
the artery. 

240 



Accidents. 241 

Hemorrhage of the Lungs or Stomach. — Blood from the lungs is 
bright, frothy, and salty ; from the stomach is usually dark and sour. 
In case of bleeding from the lungs or stomach, let the person rest 
quietly on a lounge or easy-chair. Give him some bits of ice to swallow, 
and call a physician. 

Bleeding from the Nose. — Nosebleed may sometimes be stopped by 
pressing firmly at the base of the nose. Do not lean forward, as this posi- 
tion aids the flow r . Sit up, and hold up the head, and hold a cloth under 
the nose. Apply cold water or ice to the nose and to the back of the 
neck. If this does not stop it, inject cold water, with a little salt or 
soda in it, into the nose. Often the flow may be stopped by pressing 
firmly on the upper lip at the sides of the nose. If these attempts fail, 
a long strip of cloth may be used to plug the nostril, pushing the cloth 
in a little at a time, and leaving the ends so it can be pulled out. This 
should not be removed till a long time after the flow is checked, as it 
may start the bleeding afresh. After an attack of this kind avoid blow- 
ing the nose, as this often starts bleeding again. 

Treatment of Burns. — Plunge the burned part into cold water. As 
soon as possible apply a solution of cooking soda (a tablespoonful of 
bicarbonate of soda to a teacup of water) ; or lay a wet cloth on the 
burned part and put the soda on the cloth. Afterwards apply vaseline, 
and renew the vaseline till the wound is healed. A mixture of equal parts 
of sweet oil and limewater makes a good liniment for dressing burns. 

Danger from Burning Clothing. — If the clothing takes fire, there 
is added to the danger of burning the body, the further risk of inhaling 
the flame and heated air. It is best to lie down and roll or wrap the 
body in any cloths at hand, — rugs, shawls, etc. Running serves to fan 
the flames. Hence, if a person whose clothing is on fire has lost 
presence of mind and starts to run, throw him to the ground, putting a 
wrap of some kind around the body at the same time if possible. Roll- 
ing on the ground or floor in itself would very likely put out a small 
flame. 

Treatment of Fainting. — Lay the body flat on the back. Keep the 
crowd away, and give plenty of fresh air. Loosen the clothing about the 
neck and waist. Sprinkle cold water on the face, but do not drench 
the body with a quantity of water. Apply smelling salts (ammonia) to 
the nostrils ; nib the limbs toward the body. If these remedies do not 
soon restore consciousness, send for a physician. A faint is not usually 



242 



Physiology. 



a serious matter. Bad ventilation, disagreeable odors, or even the over- 
sweet odors of such flowers as the tuberose, may cause fainting. 

Broken Bones. — Keep the patient as quiet as possible till the physi- 
cian arrives. If there is inflammation, cold water may be applied. 
Cooling applications are desirable in case of severe bruises. If it is 
necessary to carry the patient, lay him on a board, or at least keep the 
injured part as quiet as possible ; a cane or umbrella, may be tied along- 
side a leg, and supported by a pillow or a coat. Otherwise the sharp 
ends of the bones may cut the flesh or even blood-tubes. 

Sunstroke. — Lay the patient in the shade and pour cold water over 
the head. 




Fig. 106. Resuscitation from Drowning. (Lincoln, 3 Figures.) 
(Position I.) 

TREATMENT OF THE DROWNED. 

(As given by the Michigan Board of Health.) 

Rule i . Remove all obstructions to breathing. Instantly loosen or 
cut apart all neck and waist bands ; turn the patient on his face, with 
the head down hill ; stand astride the hips with your face toward his 
head, and, locking your fingers together under his belly, raise the body 
as high as you can without lifting the forehead off the ground (Fig. 
106, Position 1), and give the body a smart jerk to remove mucus from 



Accidents. 24^ 

the throat and water from the windpipe ; hold the body suspended long 
enough to count slowly, one, two, three, four, five, repeating the jerk 
more gently two or three times. 

Rule 2. Place the patient on the ground face downward, and, main- 
taining all the while your position astride the body, grasp the points of 
the shoulders by the clothing, or, if the body is naked, thrust your fingers 
into the armpits, clasping your thumbs over the points of the shoulders, 
and raise the chest as high as you can (Fig. 107, Position 2) without 
lifting the head quite off the ground, and hold it long enough to count 



Fig. 107. Resuscitation from Drowning. 
(Position 2.) 

slowly one, two, three. Replace him on the ground, with his forehead 
on his flexed arm, the neck straightened out, and the mouth and nose 
free. Place your elbows against your knees, and your hands upon the 
sides of his chest (Fig. 108, Position 3), over the lower ribs, and press 
downward and inward with increasing force long enough to count 
slowly one, two. Then suddenly let go, grasp the shoulders as before, 
and raise the chest (Position 2), then oress upon the ribs, etc. (Position 
3). These alternate movements should be repeated ten or fifteen times 
a minute for an hour at least, unless breathing is restored sooner. Use 
the same regularity as in natural breathing. 



244 



Physiology. 



Rule 3. After breathing has commenced, restore the animal heat. 
Wrap him in warm blankets, apply bottles of hot water, hot bricks, or 
anything to restore heat. Warm the head nearly as fast as the body 
lest convulsions come on. Rubbing the body with warm cloths or the 
hand, and slapping the fleshy parts, may. assist to restore warmth, and 
also the breathing. If the patient can surely swallow, give hot coffee, 
tea, milk. Alcoholic liquors are liable to produce depression. Place 




Fig. 



[08. Resuscitation from Drowning. 
(Position 3.) 



the patient in a warm bed, and give him plenty of fresh air ; keep him 
quiet. 

Avoid Delay ! — A moment may turn the scale for life or death. Dry 
ground, shelter, warmth, stimulants, etc., at this moment are nothing — 
artificial breathing is everything — is the one remedy — all others are 
secondary. Do not stop to remove wet clothing. Precious time is 
wasted, and the patient may be fatally chilled by the exposure. 

First restore Breathing. — Give all your attention and effort to re- 
store breathing by forcing air into, and out of, the lungs. If the breath- 
ing has just ceased, a smart slap on the face or a vigorous twist of the 
hair will sometimes start it again, and may be tried incidentally. 



Accidents. 245 

Before natural breathing is fully restored, do not let the patient lie on 
his back unless some person holds his tongue forward. The tongue by 
falling backward may close the windpipe and cause fatal choking. 

Prevent friends from crowding around the patient and excluding the 
fresh air ; also from trying to give stimulants before the patient can 
swallow. The first causes suffocation ; the second, fatal choking. 

Do not give up too soon : you are working for life. Any time within 
two hours you may be on the very threshold of success without there 
being any sign of it. 

Learn to Swim. — Of course, persons who cannot swim ought not to 
go out in a boat without taking along some sort of a float that may 
serve as a life-preserver. Some of the rubber cushions serve well for 
this. Every father neglects his duty if he does not teach his children, 
girls as well as boys, to swim and to float. One cool, trained person 
may save the lives of a whole boat load. 

When a Boat Upsets. — In case an ordinary rowboat is overturned, 
one should not attempt to climb into it or upon it. It takes very little 
to float a person in water, as the body is only a little heavier than 
water ; in fact, if a person fills the lungs and lies back in the water his 
face and nose will keep above water, and a person (at any rate without 
clothing) can float in this way for some time if he breathes lightly. 
Few persons have been taught these facts, and most of those who have 
learned them lose their presence of mind, and waste their breath and 
strength in wild and fruitless splashing. If a boat be overturned, those 
who can swim should help those who cannot to get hold of the edge 
of the boat, but not permit them to climb upon it. A small plank 
will float a person if he does not try to lift much of his body out of 
the water. 

Suffocation in Wells. — Persons are sometimes suffocated by carbon 
dioxid in wells and cisterns. Before going down into a well, it is a 
safe precaution to lower a lighted candle. If this is extinguished, a 
warning is given. If a second person goes down after one who has 
become unconscious, great care must be taken that two lives are not 
lost. A rope should be firmly tied about the body, a hook, attached to 
another rope, taken to catch into the clothing of the first, and the 
rescuer should be lowered quickly and brought up immediately. A 
small rope or large cord might be carried, by pulling which the signal 
is given to pull up. In resuscitating from carbon dioxid suffocation use 



246 Physiology. 

the same method as after drowning, except the first part, which is to 
remove water from the windpipe, etc. 

Poisons and their Antidotes. — Several of the common drugs and 
remedies kept about the house are more or less poisonous. The proper 
antidote for each should be known and kept at hand. In the first place, 
all such materials should be kept locked up so they will not be taken 
by children, or by mistake, as in the haste of getting medicine in the 
night. Again, all grown persons in the family should be instructed as 
to the effects of each poison, and taught its antidote. As soon as any 
new poisonous drug is bought, it should be made a point to read up 
about it, and procure an antidote. Every one should know that 
strychnin causes spasms, that opium brings on stupor, with contracted 
pupils, etc. 

Objects of Treatment. — Treatment aims at three things, (1) to get 
rid of the poison, (2) to neutralize what remains and prevent further 
action, (3) to remedy the effects already produced. 

1. Mustard a Common Emetic. — The most common emetic is mus- 
tard ; a tablespoonful in a cup of warm water ; give half of it, following 
with free drinking of warm water, then give the rest of the mustard. 
Do not wait for it to dissolve, but stir quickly and give at once. Pro- 
voke vomiting by tickling the throat with a feather or with the finger. 
If the mouth of the patient cannot readily be opened, insert the thumbs 
inside the cheeks and back of the teeth. If mustard is not at hand, a 
strong solution of table salt will serve. In a few cases, such as poison- 
ing by ammonia, lye, etc., it is considered best not to administer an 
emetic, but to try to neutralize the effect. 

2. Neutralize the Poison. — To neutralize a poison this general rule 
should be known : an alkali may be neutralized by an acid, and vice versa. 
For example, lye with vinegar, carbolic acid with alcohol and whiting 
or magnesia, etc. Some acids and alkalis are always about a house. 

3. Give Something Soothing. — After any irritant poison some mild 
and soothing substance should be given, — white-of-egg, milk, mucilage 
and water, flour and water, gruel, olive- or castor-oil. These materials 
are partly for neutralizing the poison, and are also soothing in their 
effect. If a patient is drowsy, some stimulant may be given, as strong 
coffee (after opium) . Of course a physician should be sent for imme- 
diately, as the after-treatment is of great importance. 



Accidents. 247 

Wounds from Thorns and Rusty Nails. — Promote bleeding by rub- 
bing and pressing the wound and bathing with warm water. Or suck 
the wound. This tends to remove any injurious matter. Apply 
poultices. 

Bites of Cats, Dogs, etc. — If the animal is rabid (mad), suck the 
wound and cauterize quickly. A poker or nail heated red hot is best 
for cauterizing. If one cannot do this promptly, get lunar caustic with 
which to cauterize; strong acid or alkali, or a coal of fire, may be ap- 
plied at once to the wound ; the coal on a cigar may be used. Do not 
kill the animal if there is doubt. Keep it confined, and if it proves a 
false alarm much anxiety will be saved. 

Snake Bites. — Apply ligatures around the part between it and the 
heart. Suck the wound (there is no danger in this if there are no sores 
or cracks in the skin of the mouth ; venom is not a stomach poison). 
Then apply caustics, or a live coal. Wash the wound with vinegar or 
strong salt solution. If ammonia water is at hand, add five teaspoon- 
fuls to a pint of water and drink this. Ammonium carbonate, ten per 
cent solution, is also highly recommended. A teaspoonful dose should 
be given immediately, and repeated twice at intervals of ten minutes. 
To bee stings, apply soda or dilute ammonia. 

Poison Ivy. — The itching and discomfort may be relieved by bath- 
ing the part in a mixture of two teaspoons of carbolic acid (pure), two 
tablespoons of glycerin, one half pint of water or rose-water. 

The Sick-room. — Every boy and girl ought to learn something about 
the care of the sick, as any one is likely to be called on to do this 
kind of work. Good nursing is often "half the battle." The patient 
should have a cheerful room, but the bed should be so placed that he 
will not face the light. Evidence of illness, such as medicine bottles, 
etc., should be kept out of sight so far as possible. While it is not 
best to deceive the patient as to his condition, there should at all times 
be kept up an air of cheerfulness and hope. If the physician can 
inspire with confidence, and the nurse give unflagging good cheer, the 
chances of recovery are greatly improved. Nothing sustains like hope. 
Keep the air of the room pure. Remove excreta and everything offen- 
sive just as soon as possible. Do not rely on feeling as to temperature, 
but keep a thermometer in the room. 

Sympathy with the Patient. — One of the necessary characteristics 
of a good nurse is the power of imagination. " How would I feel, and 



248 Physiology. 

what would I like to have done, if I were in his place?" This feeling 
will lead the nurse frequently to raise the patient's head and turn the 
pillow — the coolness of the other side of the pillow is refreshing; to 
give sips of cool water ; to see that the patient does not suffer for want 
of a bath. 

Bathing the Sick. — In bathing a weak person only a part of the 
body should be moistened at a time ; after this part is thoroughly dried, 
another part may be washed; it is often necessary to do all this work 
under the bed clothing. 

Changing the Bedding. — In changing the bed clothing move the 
patient to one side of the bed, push the clothing along close to his 
body, and place the clean bedding on the other side ; then move the 
patient back, remove the soiled linen, and smooth out the clean. It is 
often necessary to warm the sheets first; they should be thoroughly 
dry. 

Follow Physician's Directions Faithfully. — Have the physician's 
directions written out plainly, as they may be forgotten ; and if there is 
a change of nurses during the night there is less chance of mistake. 
Never let yourself get drowsy when acting as nurse. Get up and walk 
about, get a breath of fresh air, and if inclined to be drowsy do not 
allow yourself to settle back in an easy-chair. If watching all night, 
take a good lunch in the middle of the night ; coffee may help to keep 
you awake. 

Sweeping the Sick-room. — Do not allow the room to be swept with 
the ordinary broom. The room should have rugs that can be removed 
and shaken, and the floor wiped with a moist cloth. If the room is 
carpeted, it may be swept with moist salt, tea-grounds or coffee-grounds, 
sawdust, etc. Any dusting should be avoided ; furniture may be wiped 
with a damp cloth. 

Do not Whisper. — Do not whisper, as it disturbs more than talking, 
and also has an air of secrecy that rouses suspicion in the patient. 

Food for the Sick. — Raise the head with the hand, or bolster the 
patient up, when giving drink ; or if the patient is very weak, use a 
rubber or glass tube, so that he will not have to lift the head. The 
nurse should know how to prepare any food that may be needed during 
the night. An oil stove or gas stove is very desirable for cooking, or 
heating poultices, as an ordinary wood or coal fire is likely to die down, 



Accidents. 249 

making it impossible for the nurse to do this work quickly, as it is often 
necessary to take advantage of a favorable time, as when the patient 
wakens. 

Care of Lamps. — Most lamps, when turned low, give off a disagree- 
able gas. It is better to have a very small lamp burning at full height 
than a large one turned low ; sperm candles are recommended. Do not 
let the light shine into the patient's face. 

To Prevent Sneezing. — It is well known that a sneeze may be pre- 
vented by firmly pressing on the upper lip. This may enable a nurse 
to keep from waking a very sick patient when, at a critical point, sleep 
is almost a question of life or death. And it is a convenient fact for 
any one to know. To prevent coughing, a sip of cold or hot water will 
relieve the tickling in the throat. 

Summary. — i . To stop flow of blood from an artery apply pressure 
to the w r ound, or between the wound and the heart. 

2. To stop flow of blood from a vein apply pressure to the wound or 
beyond the heart. 

3. Leaning forward promotes, instead of checks, nosebleed. 

4. In case of a burn apply cooking soda. 

5. If the clothing takes fire, lie down and roll, or wrap a rug or shawl 
about the body. 

6. If a person with clothing on fire loses his presence of mind, seize, 
throw down, and wrap in any woolen clothing. 

7. In case of fainting lay the body flat on the back, loosen clothing, 
give fresh air, and sprinkle lightly with cold water ; if this does not 
revive, rub the limbs toward the body, hold to the nostrils smelling- 
salts (or ammonia), and send for a physician. 

8. Before going down into a well, test the air by lowering a lighted 
candle. 

9. Learn the antidotes of every poison in your house as soon as it is 
bought, and keep the antidote at hand. 

10. Volunteer to help take care of sick friends, and learn to do this 
work well. 

Questions. — i. How does holding up the wounded part check bleed- 
ing ? 

2. What other methods of resuscitation from drowning are in use ? 

3. What are some of the poisonous substances commonly kept in 
the house ? 

17 — PHY 



CHAPTER XXVII. 

VACCINATION. 

Conditions before the Discovery of Vaccination. — Before the dis- 
covery of the value of vaccination by Dr. Edward Jenner in 1796, small- 
pox was so prevalent that nearly everybody had it, and many thousands 
died from it every year, while other thousands were left blind or terribly 
scarred. Jenner discovered that persons who have had a disease called 
vaccinia, or cowpox, are much less liable to be attacked by smallpox, 
and that, if they are so attacked, the disease is not apt to be severe 
or dangerous. Before Jenner made this discovery any person who 
had had a mild attack of smallpox was considered fortunate, as those 
who have had the disease once are not liable to have it again. Since 
nearly everybody had it before Jenner's time, those who had had a 
mild attack were looked upon as having escaped a very great calamity. 
Nearly everybody in those days was scarred more or less with small- 
pox pits. It was customary when servants were employed to hire none 
who had not had smallpox, so that the employer might not be put to 
the trouble and expense of having to take care of a smallpox patient. 
So universal was smallpox and so terrible were its results that it was 
proposed, before Jenner discovered the benefits of cowpox, to inoculate 
"everybody with the virus from a mild case of smallpox, thus making 
sure that everybody should have it, in the hope that if the disease 
were thus acquired from mild cases it would be less dangerous. But 
Jenner's discovery that cowpox is a preventive of smallpox, and that 
cowpox is a comparatively harmless disease, soon changed the whole 
condition of affairs. Vaccination — that is, inoculation with the virus 
of cowpox, instead of inoculation with the virus of smallpox — became 
common. 

Value of Vaccination. — The best medical authority in every civilized 
country in the world supports the proposition that vaccination, more 
than all other causes combined, accounts for the fact that nowadays in 
those places where it is thoroughly carried out smallpox is not a preva- 

250 



Vaccination. 251 

lent disease, that very few deaths result from it, and that one seldom 
sees a person who has been disfigured by it. And there are many 
illustrations in medical literature, both in olden and in modern times, 
of the fact that, when vaccination is thoroughly practiced, smallpox 
almost entirely disappears, to break out again when vaccination has 
been neglected, and to disappear again when vaccination is resumed. 
London has furnished such illustrations many times ; and the same has 
happened in many other cities, such as Boston, Birmingham, Liverpool, 
and Montreal. In Montreal, for instance, vaccination had been generally 
practiced for many years, and there had been practically no smallpox in the 
city during that time. But, about forty years ago, many of the people 
of Montreal refused to permit their children to be vaccinated. When, 
in the winter of 1885, a colored Pullman-car porter arrived in Montreal 
sick with smallpox, the disease found a fertile field in which to spread. 
Before many months had passed thousands of the people of Montreal 
had had the disease, three thousand of them had died from it, and other 
thousands were left maimed and scarred. It was found, however, that, 
as is always the case, very few of those who had been vaccinated were 
attacked by smallpox, the disease taking as its victims almost solely 
those who had not been vaccinated. 

Harmless. — Vaccination is practically painless and harmless. The 
disease it causes, cowpox, or vaccinia, is also, compared with smallpox, 
a harmless disease. Now and then somebody dies after being vacci- 
nated. But out of the many millions who are vaccinated every year, only 
a very few die as a remote result of it. Without vaccination smallpox 
would be prevalent and kill thousands. 

Those who are opposed to vaccination claim that it does not protect 
from smallpox ; that it causes other diseases, such as tuberculosis, or 
consumption, scrofula, and tetanus, or lockjaw ; that it is more dangerous 
than smallpox, which, they claim, cannot nowadays become epidemic 
because of the greater cleanliness and better sanitary conditions which 
surround us. 

Medical Authority. — The fact still remains, however, that the best 
medical authority in all civilized countries maintains that none of the 
claims of those who oppose vaccination is founded on facts. The 
best medical authorities say that very few, if any, of the many mil- 
lions who are vaccinated every year contract consumption or other 
disease from it. They show, also, that many people die every year 



252 Physiology. 

from lockjaw as the result of infection with the lockjaw poison absorbed 
through scratches no deeper than those inflicted in vaccinating. They 
point out that any open wound may become infected with the poison of 
lockjaw. Also that, while it requires only ten days for the poison of 
lockjaw to develop, in most of the very few cases that have followed 
vaccination the disease has broken out more than ten days after the 
vaccination operation was performed. This, they claim, proves that 
the lockjaw was not the result of vaccination, but, as may happen after 
any other scratch, resulted from the lockjaw poison finding an open 
wound through which to enter the body. 

If proper care be taken thoroughly to cleanse the skin before vacci- 
nation is performed, if pure vaccine virus be used, and if the little wound 
and the vaccination sore be kept protected from infection with disease 
germs from the air, the danger from vaccination is very slight. 



CHAPTER XXVIII. 
STIMULANTS AND NARCOTICS. 

Stimulants. — A stimulant, in the physiological sense, is anything 
which causes an increase of vital activity in any of the organs of the 
body. 

Food is, therefore, a stimulant, because it increases the vital activity 
of the organs of the body. Heat and cold, in their first effects, are 
stimulants, for they increase the vital activity of the organs to which 
they are applied. To illustrate, either heat or cold will cause the skin 
first to whiten and then to redden, and heat will cause perspiration to 
flow from the sweat glands. 

Alcohol, tobacco, opium, morphine, tea, coffee and many other 
things are also stimulants, because their first action after being taken 
into the body is to increase the vital activity of some of the organs. 
All the above-mentioned stimulants affect, among other organs, the 
heart, nervous system, and brain ; arid their effects are seen first in these 
organs. 

Narcotics. — A narcotic, in the physiological sense, is anything which 
quiets the nervous system and brain, relieves pain, and produces sleep. 

All narcotics are, in their first effects, stimulants ; and all stimulants 
are, in their secondary effects, narcotics. So it may be said that stimu- 
lants are narcotics in small quantities and that narcotics are stimulants 
in large quantities. 

To illustrate again with heat and cold : one of the effects of a hot 
bath is to redden the skin, showing its stimulating effect. In a little 
while, however, the whole body becomes languorous and sleepy. One 
of the effects of cold is to redden the skin ; but, as every one knows, if 
the cold continue long enough, the person becomes drowsy and falls 
into a deep sleep. Where one *• freezes to death ,? he dies in a profound 
sleep. 

Effects of Large and Small Quantities. — Alcohol, tobacco, opium and 
morphine are all stimulants and all narcotics ; they are stimulants when 

253 



254 Physiology. 

used in small quantities and narcotics when used in large quantities. 
Thus, a glass of wine or beer sets the heart to beating more rapidly, — 
the stimulating effect ; but many glasses of either will make him who 
takes them drowsy and finally put him into a drunken sleep, — the 
narcotic effect. 

We look upon morphine and opium as examples of narcotics because 
they are used in medicines to quiet the nervous system, stop pain and 
produce sleep. Yet small doses of either have, apparently, only stimu- 
lating effects, for the reason that the various organs are able to resist 
the effects of small doses and, therefore, do not become narcotized. 

A weary horse is whipped to make him go faster or pull harder. The 
faster he goes or the harder he pulls, the more tired he becomes, and, 
therefore, the more the whipping that is necessary to keep him going. 
The whip may be called a stimulant to the tired horse, because it pro- 
duces an increase in his activity. But when the work is done, the 
horse is very tired indeed and requires a long rest before he can work 
well again. Indeed, if the horse be compelled, by the stimulating effect 
of the whip, to run or pull too hard and too long, he may fall down 
exhausted, and may even die. 

Effect of Continued Use. — Alcohol, tobacco, morphine, or opium are, 
like the whip to the horse, stimulants, in their first effects, to the bodies 
of those who use them. Like the whip also, they will, if taken in too 
great quantities, bring even death to those who use them. 

Even the most mettlesome and high-spirited horse would, if the whip 
were constantly used upon him, get so used to it that he would not 
work without being whipped. Worse than that, the more accustomed 
he gets to the whip, the more and the harder it must be used upon him, 
until, finally, he will not work unless he be whipped unmercifully all the 
time Such a horse is of no use, and his cruel master has spoiled one 
of man's best friends. 

Any person w r ho uses stimulants continuously is whipping his own 
body, as the cruel master does his horse. As in the case of the horse, 
the more the body is whipped, the more whipping it requires to make it 
do its work, until it will not work at all unless it be constantly whipped ; 
that is, constantly under the influence of stimulants. A horse that will 
not work unless it is constantly whipped is a poor sort of a horse. A 
man who will not, or cannot, work unless he is under the influence of 
stimulants is rather a poor sort of a man. We call a person cruel who 



Stimulants and Narcotics. 255 

whips his horse ; a man is cruel to himself if he allows himself to get 
Into such a condition that he must whip his body with stimulants to 
compel it to work. 

Danger in Forming Habits. — Many people drink alcoholic liquors 
and never become drunkards. Yet many people do become drunkards. 
In fact, any person, particularly one who begins in youth and who con- 
tinuously uses alcoholic liquors, is very liable indeed to become a slave 
to drink and die a drunkard. But those who continuously use alcoholic 
liquors run serious danger in other ways, even though they may never 
become drunkards. For alcohol goes into the blood when it is taken 
into the stomach, and, therefore, comes in contact with every organ of 
the body. The action of even small amounts of alcohol in the blood is 
very apt, if kept up for a long time, to produce disease of the kidneys, 
liver, stomach, heart, nerves and brain, and thus cause the death of 
those who, though never drunk, are still slaves to alcohol. These are 
well-known medical facts. 

Especially Dangerous to the Young, — The danger from stimulants is 
especially great when used by young and growing persons. They 
require all the nervous energy that their bodies produce to keep their 
organs growing besides doing their proper work. If, therefore, these 
organs be whipped by stimulants, they become accustomed to them and 
will not, or cannot, properly work without them. The result is that the 
various organs of the body, especially the heart, brain and nervous 
system, do not develop properly. Worst of all, there is the greatest 
danger that such a person will become a slave to the particular stimu- 
lant he may be using. Thus it happens that so many boys and young 
men become drunkards. They drink wine, beer and whisky; their 
growing bodies cannot withstand the effects of the stimulation, and 
finally, before they realize it, they become habitual drunkards. 

Stimulants both Unnecessary and Injurious. — That stimulants are 
not only unnecessary but even positively injurious is proven by the fact 
that no person who is training for any feat of strength, skill, or endurance, 
ever uses any of them, except, perhaps, a little weak tea or coffee. No 
one ever heard of a person training for a football or a baseball match, 
for a foot-race, for a rowing match, or for any other feat of strength, skill, 
or endurance, ever drinking any alcoholic liquors, or using tobacco, 
opium, or morphine. If they were good things, they would surely be 



256 Physiology. 

used under these circumstances where strength and endurance are re- 
quired ; if they were not injurious, they would not be prohibited. The 
cigarette is denied the college boy who is training for the college game ; 
and if he breaks the rule, he is debarred from the games because the 
trainers know that such practice on his part weakens his heart and his 
wind, and that even one cigarette may result in the loss of a closely 
contested game requiring endurance on the part of every player. 

Drunkenness. — Too much alcohol taken into the body will make the 
person who drinks it intoxicated or drunk. He staggers, sees double, 
cannot talk plainly, is foolish and silly in his talk, and cannot think 
well ; or he becomes excited and violent, wants to fight, imagines that 
he is being insulted, and, crazed as he is, sometimes even kills his best 
friend. 

After a while the drunken man, like the whipped horse, becomes 
exhausted. His muscles, his brain and his whole body are tired out by 
the extra work the stimulants have made them do, and he falls into a 
drunken sleep, from which he cannot be easily aroused ; the narcotic 
effect of the alcohol has shown itself. Indeed, it not infrequently hap- 
pens that the poor drunkard does not wake up at all ; but his heart and 
brain, worn out by the over-stimulation of the alcohol he has drunk, 
stop working, and he dies, like the horse which has been lashed beyond 
his strength by his cruel driver. 

How often it happens that drunken men commit murder ; many 
railroad accidents, bringing death or terrible injuries to thousands of 
people, have been due to the alcohol-beclouded brains of engineers, 
switchmen and train dispatchers. Our prisons and jails are crowded 
with convicts, most of them young men, who committed some crime 
while under the influence of liquor, not necessarily drunk, maybe having 
taken only a glass or two. Railroad, bank, and steamship companies, 
which are responsible for lives and property, have found, by experience 
that it is not safe to employ men who use liquor habitually, even though 
they never become intoxicated. 

Criminals. — The great majority of our criminals, a large share of pur 
insane, very many of our deaths, most of our murders, practically all the 
poverty, want, starvation and sickness in the crowded portions of our 
cities, are due directly or indirectly to the use of liquor. 

Many people, it is true, drink wine and beer and even whisky and 



Stimulants and Narcotics. 257 

never become drunkards. But any boy or young man who does this 
runs a great risk of becoming a slave to alcohol and ruining his health, 
even if he does nothing worse. 

Tobacco. — Tobacco, like alcohol, is both a stimulant and a narcotic ; 
it affects the heart and the nervous system. It is not so dangerous to life 
as alcohol ; it does not fill our jails and insane asylums as alcohol does. 
But it is particularly injurious to the growing boy. It weakens his heart 
and disturbs his nervous system and dulls his brain. 

Many boys use tobacco and think that it does them no harm. But 
let them go to a doctor and have their hearts examined, and it will be 
found that that organ is weaker than it should be. If tobacco-using 
boys are attacked by such diseases as typhoid fever or pneumonia, they 
are much more liable to die from heart failure than if they had not used 
tobacco. Such boys cannot run so fast nor so far, play marbles, foot- 
ball, or baseball so w 7 ell or do any athletic feat so skillfully, as they 
could if they did not use tobacco. These are well-established medical 
facts, so well known that no person who is training boys or men for 
any game or athletic event will permit any of those under his care to 
use tobacco in any form. 

Grown-up people can use tobacco, as they can alcohol, with less danger 
to themselves than growing boys can. But even adults who use tobacco 
are liable to have weak hearts. In fact, many men are refused life in- 
surance because their hearts are weakened by tobacco. Such men are 
liable to die from heart failure if they run for a street car or make 
any unusual exertion, and pneumonia or any other severe attack of ill- 
ness is liable to kill them. 

It is true some boys use tobacco and do not appear to be injuri- 
ously affected by it, and many men use it and die of old age. But it 
is the fact, nevertheless, and all medical men will bear witness to the 
truth of it, that many boys ruin their health by using tobacco, and that 
no boy can be so strong, so quick, so skillful at his games, or so easily 
get through school, if he smokes cigarettes or uses tobacco in any form. 
If these things are true, and they are true, any boy who uses tobacco is 
foolish. 

To this many boys will reply, " Isn't a man who uses tobacco fool- 
ish?" Yes, he is. But the danger and damage from tobacco to the 
growing boy are greater than to the grown man, simply because the boy 
is growing and the man is grown. 



258 Physiology. 

Opium. — Opium is the dried juice of a certain kind of poppy. It 
contains a number of different substances, one of which is morphine, to 
which it principally owes its narcotic and stimulant effects. 

Opium is used by the people of some nations as a stimulant. The 
Chinese, for instance, are addicted to the vice, and many of our people 
have learned from them to smoke opium. Most of our confirmed 
criminals, the poor outcasts who spend most of their lives in prison, are 
slaves to the alcohol and opium habits. In almost every Chinatown in 
California may be found rooms where opium is smoked by white people, 
and most of the poor victims of this terrible habit are youths and young 
men. This is so because grown people seldom get close enough to the 
Chinese to acquire the habit, only idle boys and youths having time and 
inclination to loiter about the Chinese quarters. Those who learn to use 
opium soon resort to crime to get money with which to buy the deadly 
stuff, and soon go to jail, or else die. So that the white patrons of the 
opium dens are mostly young people. 

It is pitiable, as well as disgusting, to see the poor fools who have 
become opium smokers. They have lost all sense of shame and are 
content to associate with the Chinese in their dirty, ill-smelling houses. 
They will borrow from their friends, if they have any, beg upon the 
streets, lie, steal, do almost anything that is shameful, in order to get a 
little money with which to buy opium. They are pale, trembling and 
haggard ; their clothes are dirty and ragged, and they soon go to prison 
for stealing, or as common vagrants, or they die. 

A certain small proportion of those who use alcohol to excess reform ; 
but one who becomes a slave to opium seldom if ever reforms. Like 
the horse that is used to the whip, his organs will not work without 
being lashed by the stimulating effects of the opium. If he be deprived 
of it, he cannot eat, and is nervous and ill-tempered. He cannot go to 
sleep until he is worn out, and when he does doze off he has horrible 
dreams. He cannot work, read, or enjoy himself in any way. All that 
he thinks about is opium. He aches in every bone and muscle and nerve, 
and his sufferings become so intense that he will stoop to any meanness 
or commit almost any crime to obtain the stuff that has deprived him of 
his manhood and made him a slave to a more cruel and unrelenting 
master than he who whips his poor horse to death. 

Morphine. — Morphine is also used as a stimulant. The morphine user 
is, like the opium user, an absolute slave to the habit. Once begun, the 



Stimulants and Narcotics. 259 

use of the stuff is very rarely if ever stopped. Its victims cannot work 
without it and soon become so unreliable that no one will employ them. 
Yet both opium and morphine are medicines of the greatest value 
when used by physicians for the cure of disease. But used for any 
other purpose, or without the direction of a physician, they are deadly 
poisons, sure to bring those who use them to the lowest depths of 
degradation, sure to make them criminals and beggars, sure to send 
them down to shameful deaths and paupers 1 graves. 

MILDER STIMULANTS. 

Tea, Coffee and Cocoa, or Chocolate, are mild stimulants. But even 
they, when used to excess, may produce various nervous troubles. They 
act upon the heart and nervous system, and, like all other stimulants, 
should be carefully avoided by the young and growing. 

PATENT MEDICINES. 

There are many people who, though opposed to the use of alcoholic 
beverages of any kind, do not hesitate to take, as medicine, so-called 
u bitters " and other patent medicines, many of which contain alcohol 
in great or less quantities, and which, therefore, are as intoxicating as 
wine or beer or even w r hisky. Such people think that their health is 
bad ; and they ascribe to " the medicine " the temporary stimulating 
effect of the alcohol, which, unknown to themselves, they are taking. 
Unconsciously they take more and more of the stuff, not realizing that 
they are becoming addicted to the liquor habit just as much as if they 
were drinking any other alcoholic liquors. 

Such people would be very indignant if they were told that they were 
doing that which they condemn in others; viz., drinking intoxicating 
liquors. Yet such is the fact, and the worst part of it is that the alcohol 
usually found in such so-called " medicines 1 ' is of the cheapest, most 
poisonous kind, and, therefore, like the cheapest wines, beers, and 
whiskies, is very destructive to health. 



GLOS SAET. 



Albumen (al-bu'-men). The white of an egg. 

Albumin (al-bu'-min). A proteid substance, the chief constituent of 
the body. Its molecule is highly complex, and varies widely within 
certain limits in different organs and in different conditions. 

Albuminuria (al-bu'-mi-nu'-ri-a). The presence of albumin in the urine, 
indicating changes in the blood or in the kidneys. 

Amylopsin (am-i-lop'-sin) . A ferment said to exist in pancreatin. 

Anabolism (an-ab'-o-lizm) . Synthetic or constructive metabolism. 
Activity and repair of function ; opposed to katabolism. 

Arbor Vitae (ar'-bor vi'-te). A term applied to the branched appear- 
ance of a section of the cerebellum. 

Argon (ar'-gon). A newly discovered element similar to nitrogen 
(found in the air). 

Arytenoid (ar-i-te'-noid) . Resembling the mouth of a pitcher, as the 
arytenoid cartilages of the larynx. 

Atlas (at'-las). The uppermost of the cervical vertebrae (from the 
mythical Atlas who supported the Earth). 

Auricle (aw'-ri-kl). The auricles of the heart are the two cavities be- 
tween the veins and the ventricles. Also*, the pinna and external 
meatus of the ear. 

Axis (ak'-sis). The second cervical vertebra, on which the head, with 
the atlas, turns. 

Bacterium (bak-te'-ri~um) , pi. bacteria. A genus of microscopic fungi 
characterized by short, linear, inflexible, rod-like forms — without 
tendency to unite into chains or filaments. 

Biceps (bi'-seps). Biceps brachii, the flexor of the arm. 

Bicuspid (bi-kus'-pid.). Having two points ; the bicuspid or premolar 
teeth; the bicuspid valve, between the left auricle and the left ven- 
tricle. 

Brachial (bra'-ke-al or brak'-i-al). Pertaining to the arm. 

261 



262 Glossary. 



Bronchus (brong'-kus), pi. bronchi. The two tubes into which the tra- 
chea divides opposite the third thoracic vertebra, called respectively 
the right and left bronchus. 

Caffein (kaf'-e-in). An alkaloid that occurs in the leaves and beans of 
the coffee-tree, in Paraguay tea, etc. 

Canaliculus (kan-a-lik'-u-lus), pi. canaliculi. The crevices extending 
from lacunae, through which nutrition is conveyed to all parts of 
the bone. 

Canine (ka-nin' or kd'-riin). The conical teeth between the incisors 
and the premolars. 

Capillary (kap' -i-ld-ri or ka-piV-a-ri). A minute blood-tube connecting 
the smallest ramification of the arteries with those of the veins. 

Capsule (kap'-sul). A tunic or bag that incloses a part of the body or 
an organ. 

Carbohydrate (kar-bo-hi'-drdt). An organic substance containing six 
carbon atoms or some multiple of six, and hydrogen and oxygen in 
the proportion in which they form water; that is, twice as many 
hydrogen as oxygen atoms. Starches, sugars, and gums are carbo- 
hydrates. 

Cardiac (kar'-di-ak). Pertaining to the heart. 

Carotid (ka-rot'-id). The principal right and left arteries of the neck. 

Carpus (kar'-pus). Belonging to the wrist; as the carpal bones. 

Cartilage (kar'-ti-laj). Gristle of various kinds, articular, etc. 

Casein (kaf-se-iii). A derived albumin, the chief proteid of milk, pre- 
cipitated by acids and by rennet at 40°C. 

Cecum (se'-kum). The large blind pouch or cul-de-sac, in which the 
large intestine begins. 

Centrum (sen'-trum). The center or middle part ; the body of a verte- 
bra, exclusive of the bases of the neural arches. 

Cerebellum (ser-e-bel'-um). The inferior part of the brain, lying below 
the cerebrum. 

Cerebrum (ser'~e-brwri). The chief portion of the brain, occupying the 
whole upper part of the cranium. 

Cervical (ser'-vi-kal). Pertaining to the neck, as cervical vertebrae. 

Chordae tendineae (kor'-de). The tendinous cords connecting the 
fleshy columns. of the heart with the auriculo-ventricular valves. 

Choroid (ko'-roid). The second or vascular coat of the eye, continu- 
ous with the iris in front, and lying between the sclerotic and the 
retina. 



Glossary. 263 



Chyle (kV). The milk-white fluid absorbed by the lacteals during di- 
gestion. 

Chyme (fctm). Food that has undergone gastric digestion, and has not 
yet been acted upon by the biliary, pancreatic, and intestinal 
secretions. 

Cilium (sil'-i-um), pi. cilia. The eyelashes ; also the hair-like appen- 
dages of certain epithelial cells, whose function is to propel fluid 
or particles along the passages that they line. 

Ciliary (sil'-i-a-ri). Pertaining to the eyelid or eyelash ; also by ex- 
tension to the ciliary apparatus or the structure related to the 
mechanism of accommodation. Pertaining to the cilia, 

Circumvallate (sir-kum-val'-at). Surrounded by a wall or prominence, 
as the circumvallate papillae on the tongue. 

Clavicle (klav'-i-kl). The collar-bone. 

Coccyx (kok'-siks). The last bone of the spinal column, formed by the 
union of four rudimentary vertebrae. 

Cochlea (kok'-le-a). A cavity of the internal ear, resembling a snail- 
shell. 

Conjunctiva (kon-jungk-ti'-va). The mucous membrane covering the 
anterior portion of the globe of the eye, reflected on, and extending 
to, the free edge of the lids. 

Corpus Arantii (kor'-pus). The tubercles, one in the center of each 
segment of the semilunar valves. 

Corpuscle (kor'-pus-l). A name loosely applied to almost any small, 
rounded or oval body, as the blood corpuscles. 

Cortex (kor'-teks). Bark. The outer layer of gray matter of the brain ; 
the outer layer, cortical substance, of the kidney. 

Cricoid (kri'-koid). Ring-shaped, as the cricoid cartilage of the 
larynx. 

Dentine (den'-tiri). The ivory-like substance constituting the bulk of 
the tooth, lying under the enamel of the crown and the cement 
of the root. 

Diabetes (di-a-be'-tez). The name of two different affections, diabetes 
mellitus, or persistent glycosuria, and diabetes insipidus, or polyu- 
ria, both characterized, in ordinary cases, by an abnormally large 
discharge of urine. The former is distinguished by the presence 
of an excessive quantity of sugar in the urine. 

Dialysis (di-al';i-sis). The operation of separating crystalline from 
colloid substances by means of a porous diaphragm, the former 



264 Glossary. 

passing through the diaphragm into the pure water upon which the 
dialyzer rests. 

Digastric (di-gas'-trik). Having two bellies, as the digastric muscle, 
enlarged near each end and with a tendon in the middle. 

Duodenum (du-o-de'-num). The first part of the small intestine, begin- 
ning with the pylorus. 

Emulsion (e-mul'-shun). Water or other liquid in which oil, in minute 
subdivision of its particles, is suspended. 

Enamel (en-am' -el). The hard covering of the crown of a tooth. 

Endothelium (en-do-the'-li-um). The internal lining membrane of 
serous, synovial, and other internal surfaces, the homolog of epi- 
thelium. 

Enzyme (en'-zim). Any chemic or hydrolytic ferment, as distinguished 
from organized ferments such as yeast; unorganized ferment. 

Epiglottis (ep-i-glot'-is). A thin fibrocartilaginous valve that aids in 
preventing food and drink from passing into the larynx. 

Esophagus (e-sof'-a-gus). The musculo-membranous tube extending 
from the pharynx to the stomach. 

Eustachian (n-sta'-ki-an). Eustachian tube, the tube leading from the 
middle ear to the pharynx. 

Facet (fas'-et). A small plane surface. The articulating surface of a 
bone. 

Femur (fe'-mer). The thigh-bone. 

Ferment (fer'-ment). Any micro-organism, proteid, or other chemic 
substance capable of producing fermentation, i.e., the oxidation 
and disorganization of the carbohydrates. 

Fibrin (fi'-brin). A native albumen or proteid, a substance that, be- 
coming solid in shed blood, plasma, and lymph, causes coagulation 
of these fluids. 

Fibula (fib'-u-la). The smaller or splint bone in the outer part of the 
leg, articulating above with the tibia, and below with the astraga- 
lus and tibia. 

Filiform (fil'-i-form). Thread-like, as the filiform papillae. 

Frontal (fron'-tal). Belonging to the front, as the frontal bone. 

Fungiform (fun'-ji-form). Having the form of a mushroom, as fungi- 
form papillae. 

Ganglion (gang'-gli-on), pi. ganglions or ganglia. A separate and semi- 
independent nervous center, communicating with other ganglia or 
nerves, with the central nervous system, and peripheral organs. 



Glossary. 265 



Gastric (gas'-trik). Pertaining to the stomach. 

Gelatin (jel'-a-tin). An albuminoid substance of jelly-like consistence, 
obtained by boiling skin, connective tissue, and bones of animals 
in water. The glue of commerce is an impure variety. 

Glosso-pharyngeal (glos'-o-fa-rin'~je-al). Pertaining to the tongue and 
larynx. 

Gluten (glo'-ten). A substance resembling albumin, and with which it 
is probably identified ; it occurs abundantly in the seeds of cereals. 

Glycogen (yli'-ko-jen). A white amorphous powder, tasteless and odor- 
less, forming an opalescent solution with water, and insoluble in 
alcohol. It is commonly known as animal starch. It occurs in the 
blood and rn the liver, by which it is elaborated, and is changed by 
diastasic ferments into glucose. 

Gustatory (gus'-ta-to-ri). Pertaining to the special sense of taste and 
its organs. 

Hashish (hash'-esh). A preparation from Indian hemp, Cannabis in- 
dica. It is a powerful narcotic. 

Haversian (ha-ver'-zian). Haversian canal, in bone, a central opening 
for blood-tubes, surrounded by a number of concentric rings, or 
lamellae, of bone. 

Hemoglobin (hem-o-glo'-bin). A substance existing in the corpuscles of 
the blood, and to which their red color is due. 

Hepatic (he-pat'-ik). Pertaining or belonging to the liver. 

Hilum (Jii'-lum). A small pit, scar, or opening in an organic structure ; 
the notch on the internal or concave border of the kidney. 

Humerus (hu'-me-rus) . The bone of the upper arm. 

Humor (hu'-mor). Any liquid, or semi-liquid, part of the body. 

Hyoid (hi'-oid). Having the form of the letter U. The hyoid bone 
situated between the root of the tongue and the larynx, supporting 
the tongue and giving attachment to its muscles. 

Hypo-glossal (hi-pd-glos'-al). Under the tongue. 

Iliac (il'-i-ak). Pertaining to the ilium, or region of the flanks, as iliac 
artery, vein, etc. 

Incisor (in-si'-sor). The chisel-shaped front teeth. 

Inhibition (in-M-bish'-nn). The act of checking, restraining, or sup- 
pressing ; any influence that controls, retards, or restrains. Inhib- 
itory nerves and centers are those intermediating a modification, 
stoppage, or suppression of a motor or secretory act already in 
progress. 



18 — PHY 



266 Glossary. 

Innominate (i-nom'-i-nate). Nameless ; a term applied to several parts 
of the body to which no other definite name has been given, as the 
innominate bone, artery, vein, etc. 

Invertin (in'-ver-tin). A ferment found in the intestinal juice, and also 
produced by several species of plants ; it converts cane-sugar in 
solution into invert sugar. 

Jugular (jo'-gu-lfir). Pertaining to the throat, as the jugular vein. 

Katabolism (ka~tab'-d-lizm) . Analytic or destructive metabolism ; a 
physiologic disintegration ; opposed to anabolism. 

Lacrymal (lak'-ri-mal). Having relation to the organs of the secretion, 
transfer, or excretion of tears. 

Lacuna (la-ku'-na). A little hollow space ; especially the microscopic 
cavities in bone occupied by the bone corpuscles, and communicat- 
ing with one another and with the haversian canals and the sur- 
faces of the bone through the canaliculi. 

Lamella (la-meV-a\ pi. lamellae. A thin lamina, scale, or plate ; of 
bone, the concentric rings surrounding the haversian canals. 

Larynx (lar'-ingks). The upper part of the air passage between the 
trachea and the base of the tongue ; the voice-box. 

Legumin (le-gu'-miii). A proteid compound in the seeds of many plants 
belonging to the natural order Leguminosae (peas, beans, lentils, 
etc.).' 

Lumbar (lum'-bar), pertaining to the loins, especially to the region 
about the loins. 

Lymphatic (lim-fat'-ik). Pertaining to lymph. 

Lymphatics (lim-fat'-iks). The tubes that convey lymph. 

Lymphatic glands. The glands intercalated in the pathway of the 
lymphatic tubes, through which lymph is filtered. 

Massage (ma-sazh'). A method of effecting changes in the local and 
general nutrition, action and other functions of the body, by rub- 
bing, kneading, and other manipulation of the superficial parts of 
the body by the hand or an instrument. 

Masseter (mas'-e-ter). A chewing-muscle felt on the angle of the 
jaw. 

Medullary (med'-u-la-ri). Pertaining to the medulla, or marrow ; re- 
sembling marrow. Also pertaining to the white substance of the 
brain contained within the cortical envelop of gray matter. 

Mesenteric (mez-en-ter'-ik). Pertaining to the mesentery, as artery, 
vein, etc. 



Glossary. 267 



Mesentery (mcz'-cn-tcM). A fold of the peritoneum that connects cer- 
tain portions of the intestine with the dorsal abdominal wall. 

Metabolism {me-tab'-o-lizm). A change in the iirtimate condition of 
cells ; (1) constructive or synthetic metabolism is called Anabo- 
lism ; in anabolism, the substance is becoming more complex and 
is accumulating force ; (2) destructive or analytic metabolism is 
called Katabolism ; in katabolism there is disintegration, the mate- 
rial is becoming less complex, and there is loss or expenditure of 
force. 

Metacarpus (met-a-kiir'-pus). The bones of the palm of the hand. 

Metatarsus (met-a-tiir'-sus). The five bones of the arch of the foot, 
situated between the tarsus and the phalanges. 

Mitral (mi'-tral). Resembling a miter; mitral valve, with two flaps, 
between the left auricle and the left ventricle. 

Molar (mo'-lar). Mill; the grinding-teeth. 

Mucous (mu'-kus). A term applied to those tissues that secrete mucus. 

Mucus (mu'-kus). A viscid liquid secretion of mucous membranes, 
composed essentially of mucin, holding in suspension desquamated 
epithelial cells, etc. 

Myosin (mi'-o-sin). A proteid of the globulin class, — the chief proteid 
of muscle. Its coagulation after death causes rigor mortis. 

Narcosis (nar-ko'-sis). The deadening of pain, or production of incom- 
plete or complete anesthesia by the use of narcotic agents, such as 
anesthetics, opium, and other drugs. 

Narcotic {nar-kot'-ic). A drug that produces narcosis. 

Neural (nu'-ral). Pertaining to the nerves. 

Neuroglia (nu-rog'-li-a). The reticulated framework or skeleton-work 
of the substance of the brain and spinal cord. The term is some- 
times abbreviated to glia. 

Nucleus (nu'-kle-us). The essential part of a typical cell, usually round 
in outline, and situated in the center. 

Occipital (ok-sip'-i-tal). Pertaining to the occiput or back part of the 
head, as the occipital bone. 

Odontoid (o~don'-toid). Resembling a tooth ; the tooth-like process 
(axis) of the second cervical vertebra, on which the atlas turns. 

Olfactory (ol-fak'-to-ri'). Pertaining to the sense of smell. 

Osmosis (os-mo'-sis). That property by which liquids and crystalline 
substances in solution pass through porous septa; endosmosis and 
exosmosis. 



268 Glossary 



Oxy-hemoglobin (ok-si-hem-d-glo'-bin). Hemoglobin united, molecule 
for molecule, with oxygen. It is the characteristic constituent of 
the red corpuscles to which the scarlet color of arterial blood is 
due. 

Pancreas (pan'-kre-ds). A large racemose gland lying transversely 
across the dorsal wall of the abdomen. It secretes a clear liquid 
for the digestion of proteids, fats, and carbohydrates. The sweet- 
bread of animals, vulgarly called the "belly sweet-bread" in con- 
tra-distinction to the thymus, or true sweet-bread. 

Pancreatin (pan'-kre-a-tin). The active element of the pancreatic juice. 

Papilla (pa-pil'-a), pi. papillae. Any soft, conical elevation, as papillae 
of the dermis, tongue, etc. 

Papillary (pap'~i-la-ri). Pertaining to a papilla; papillary muscles,— 
the conic muscular columns of the heart, to which the chordae 
tendineae are attached. 

Parietal (pa-ri'-e-tal). Pertaining to the walls, as the parietal bone. 

Parotid (pa-rot' -id). 2sear the ear, as the parotid salivary glands. 

Patella (pa-tel'-a). The knee-pan. 

Peptone (pep'-ton). A proteid body produced by the action of peptic 
and pancreatic digestion. 

Pericardium (per-i-kar'-di-mii) . The closed membranous sac or cover- 
ing that envelops the heart. 

Periosteum (per-i-os'-te-um). A fibrous membrane that invests the 
surfaces of the bones, except at the points of tendinous and liga- 
mentary attachments, and on the articular surfaces where cartilage 
is substituted. 

Peristaltic (per-i-stal'-tik). The peculiar movement of the intestine 
and other tubular organs, consisting in a vermicular shortening 
and narrowing of the tube, thus propelling the contents onward. 
It is due to the successive contractions of the bundles of longitudi- 
nal and circular muscular fibers. 

Peritoneal (per-i-to-ne'-al). Pertaining to the peritoneum. 

Peritoneum (per-i-to-ne'-um'). The serous membrane lining the interior 
of the abdominal cavity, and surrounding the contained viscera. 
The peritoneum forms a closed sac, but is rendered complex in its 
arrangement by numerous foldings produced by its reflection upon 
the viscera. 

Phalanges (fa-lan'-jez), plural of phalanx (fa'-langks). Any one of 
the bones of the fingers or toes. 



Glossary. 269 



Pharynx (far'-tnrjJis). The cavity back of the soft palate. It commu- 
nicates anteriorly with the posterior nares, laterally with the eusta- 
chian tubes, ventrally with the mouth, and posteriorly with the 
gullet and larynx. 

Plasma (platf-ma). The original undifferentiated substance of nascent, 
living matter. The fluid part of the blood and lymph. 

Pleura (j&Zo'-ra). The serous membrane which envelops the lungs, and 
which, being reflected back, lines the inner surface of the thorax. 

Plexus (plek'-sus). An aggregation of vessels or nerves forming an 
intricate net-work. 

Pneumogastric (nu-mo-gas'-trik). Pertaining conjointly to the lungs 
and the stomach, or to the pneumogastric or vagus nerve. 

Portal (jpor'~tal). Pertaining to the porta (gate) or hilum of an organ, 
especially of the liver, as the portal vein. 

Postcaval (post-kd'-val). Pertaining to the posteava; the postcaval 
vein, formerly called the inferior vena cava, or vena cava ascendens. 

Precaval (pre-ka'-val). Pertaining to the precava; the anterior caval 
vein, formerly called the superior vena cava, or vena cava de- 
scendens. 

Pronation (pro-na'-shun). The turning of the palm downward. 

Protoplasm (pro'-tb-plazm). An albuminous substance, ordinarily re- 
sembling the white of an egg, consisting of carbon, oxygen, nitro- 
gen, and hydrogen in extremely complex and unstable molecular 
combination, and capable, under proper conditions, of manifesting 
certain vital phenomena, such as spontaneous motion, sensation, 
assimilation, and reproduction, thus constituting the physical basis 
of life of all plants and animals. 

Ptyalin (ti'-a-lin). An amylolytic or diastasic ferment found in saliva, 
having the property of converting starch into dextrin and sugar. 

Pulmonary (pul'-mo-na-ri). Pertaining to the lungs. 

Pylorus (pi-Id' -mis). The opening of the stomach into the duodenum, 

Radius {rd'-di-us). The outer of the bones of the forearm. 

Renal (re'-nal). Pertaining to the kidneys. 

Rennin (ren'-in). An enzyme, or ferment, to whose action is due the 
curdling or clotting of milk produced upon the addition of ren- 
net. 

Retina (ret'-i-na). The chief and essential x^eripheral organ of vision; 
the third or internal coat or membrane of the eye, made up of the 
end organs or expansion of the optic nerve within the globe. 



270 Glossary. 



Sacrum (sa'-krum). A curved triangular bone, composed of five con- 
solidated vertebrae, wedged between the two iliac (pelvic) bones, 
and forming the dorsal boundary of the pelvis. 

Scapula (skap'-u-la). The shoulder-blade. 

Sciatic (si-al'-ik). Pertaining to the ischium; the sciatic nerve, the 
main nerve of the thigh. 

Sclerotic (skle-rot'-ik). Hard, indurated; pertaining to the outer coat 
of the eye. 

Semilunar (sem-i-lu'-nar). Kesembling a half-moon in shape; semilu- 
nar valves, pocket-like valves at the beginning of the aorta and 
pulmonary artery. 

Serous (se'-rus). Pertaining to, characterized by, or having the nature 
of, serum. 

Serum (se'-rum). The yellowish fluid separating from the blood after 
the coagulation of the fibrin. 

Solar plexus (so'-lar). Solar, with radiations resembling the sun. 

Sphincter (sfingk'-ter). A muscle surrounding and closing an orifice. 

Splenic (splen'-ik). Pertaining to the spleen. 

Steapsin {step' -sin). A diastasic ferment which causes fats to combine 
with an additional molecule of water and then split into glycerine 
and their corresponding acids. 

Sternum (ster'-num). The breast-bone. 

Subclavian (sub-kla'-vi-an). Situated under the collar-bone ; subcla- 
vian artery and vein. 

Sublingual (sub-ling' -gwal). Lying beneath the tongue, as sublingual 
gland. 

Submaxillary (sub-mak'-si-la-ri). Lying beneath the lower maxilla, as 
submaxillary salivary gland. 

Supination (su-pi-nd'-shun). The turning of the palm upward. 

Synovia (si-no'-vi-a). The lubricating liquid secreted by the synovial 
membranes in the joints. 

Tarsus (tar'-sus). The instep, consisting of seven bones. 

Temporal (tem'-po-ral). Pertaining to the temples, as temporal artery, 
vein, muscle, etc. 

Tetanus (tet'-a-nus). A spasmodic and continuous contraction of the 
muscles, causing rigidity of the parts to which they are attached. 

Thein (the'-in). An alkaloid found in tea. 

Theobromin (the-o-bro' '-ram) . A feeble alkaloid obtained from cacao- 
butter ; the essential substance found in cocoa and chocolate. 



Glossary. 271 



Thyroid (thi'-roid). Shield-shaped, as the thyroid cartilage of the 
larynx. 

Tibia (tib'-i-a). The larger (inner) of the two bones of the leg, com- 
monly called the shinbone. 

Trachea (tra-kef-a or tra'-ke-a). The windpipe. 

Triceps (tri'-scps). Triceps of the arm, the extensor of the arm, lying 
along the back of the humerus. 

Tricuspid (trl-kus'-pid). Having three cusps or points, as the tricuspid 
valve. 

Trypsin (trip' -sin). The proteolytic ferment of pancreatic juice. 

Ulna (ul'-nd). The larger (inner) of the two bones of the forearm. 

Ureter (u-re'-tcr). The tube conveying the urine from the pelvis of the 
kidney to the bladder. 

Vaso-constrictor (vas'-o-kon-strik'-tor). Causing a constriction of the 
blood-vessels. 

Vaso-dilator (vas'-o-di-la'-tor). Pertaining to the positive dilating mo- 
tility of the non-striated muscles of the vascular system. 

Vaso-motor (vas-o-mo'-tor). Serving to regulate the tension of the 
blood-vessels, as vaso-motor nerves ; including vaso-dilator and 
vaso-constrictor mechanisms. 

Ventricle (ven'-tri-kl). Applied to certain structures having a bellied 
appearance. The cavities of the heart from w r hich the blood is 
forced out through the arteries. 

Vesicle (ves'-i-kl). A small, membranous, bladder-like formation, as 
air vesicle. 

Villus (vil'-us), pi. villi. One of the numerous minute vascular projec- 
tions from the mucous membrane lining the small intestine, for ab- 
sorbing digested food. 

Vitreous (vit'-re-us). Glass-like^ as the clear, jelly-like, vitreous humor 
of the eye. 



INDEX. 



Absorption, 172-180. 
Accidents, 240-249. 
Accommodation, 218, 225. 

Muscle of, 225, 226, 227. 
Adam's apple, 237. 
Adenoids, 95. 
Air, composition of, 97. 

Effects of rebreathing, 103. 

Washed by rain, 114. 

Washed by snow, 114. 
Albinos, 125. 
Albumen, 145. 
Albuminuria, 187. 
Alcohol, action in blood, 255. 

Cause of crime, 256. 

Cause of death, 256. 

Cause of railroad accidents, 256. 

Compared with tobacco, 257. 

Effect of continued use, 254. 

And employers, 256. 

And exhaustion, 256. 

A narcotic, 253, 256. 

A stimulant, 253, 254. 

Temporary effect of, 256. 
Alcoholic liquors, 254, 255, 256. 

And athletics, 255. 

Continuous use of, 255. 

And criminals, 256. 

Dangerous for the young, 255. 
Amylopsin, 166. 
Anatomy, defined, 2. 
Anti-toxin, 120. 
Anvil, 235. 
Aorta, 52, 176. 
Apoplexy, 206. 



Appendix, vermiform, 168, 169. 
Aqueous humor, 218. 
Arteries, action of, 57-59. 

Blood flow in, 64, 65. 

Structure of, 58, 59, 62. 
Artificial respiration, 243, 244. 
Asiatic cholera, 116. 
Assimilation, 185. 
Astigmatism, 229. 
Atlas, 10. 
Auricle, 48-57. 
Axis, 10. 

Bacilli, kinds of, 1 1 7. 
Bacteria, 1 18. 
Baking, 144. 
Barley, 138. 
Baseball, 194. 
Bathing, 195-197. 

The sick, 248. 
Bee stings, 247. 
Beef tea, 144. 
Beer, 254, 255, 259. 
Bicycling, 195. 
Bile, 164. 
Bites of cats and dogs, 247. 

Of snakes, 247. 
Bitters, 259. 

Black-and-blue spots, 77. 
Bleeding, from arm, 240. 

From arteries, 240. 

From lungs, 241. 

From neck, 240. 

From nose, 241. 

P^rom stomach, 241. 

273 



274 



Index. 



From thigh, 240. 

From veins, 240. 
Blind spot, 219. 
Blister, 125. 
Blood, 74-77. 

Amount of, 77. 

Poisoning, 116. 
Blushing, 69. 
Boats upsetting, 245. 
Body and candle, 97, 98. 

And locomotive, 102, 103. 

And stove, 102. 
Boiling, 144. 
Boiling water, 141. 
Bones, 5-14. 

Broken, 14, 34, 242. 

Composition of, 12, 13. 

In ear, 235. 

Structure of, 12, 31. 
Boxing, 194. 
Brain, 36, 37, 198-206. 

Blood supply of, 206. 

Functions located, 203. 

Rest, 205. 

Work, 205. 
Broiling, 144. 
Bronchus, 86. 
Burns, 241. 

Candle, oxidation of, 97, 98. 

Capillaries, blood flow in, 60, 61. 

Carbohydrates, 137. 

Carbon dioxid, 97, 103. 

Carpets, 118. 

Carpet sweepers, patent, 1 19. 

Cartilage, 10, 32, 90, 91. 

Cecum, 168. 

Cellars, ventilation of, 112. 

Cells, 3. 

Of blood, 74. 

Of brain, 201. 

Of epidermis, 61. 

Of ganglions, 41, 42. 

Of glands, 153. 



Of lymph, 78. 

Of muscle, 19, 20. 
Cellulose, 144. 
Cerebellum, 198, 199, 200. 

Function of, 204. 
Cerebrospinal nervous system, 37. 
Cerebrum, 198. 
Cesspools, 140, 141. 
Cheese, 136. 
Chocolate, 259. 
Choking, 92. 
Choroid coat of eye, 217. 
Chyle, 174, 175. 

Receptacle of, 78. 
Chyme, 161. 

Cigarette smoking, 256, 257. 
Ciliary muscle, 225. 
Ciliums, 85. 
Circulation and clothing, 72. 

Control of, 67. 

In frog's web, 60, 61. 
Clot, 80, 81. 

Coagulation of blood, 76, 77. 
Coccyx, 10. 
Cochlea, 235, 236. 
Cocoa, 259. 
Coffee, 253, 255, 259. 
Colds and deafness, 237. 

Taking, 195. 
Colon, 167, 168. 
Color blindness, 221. 
Color of eyes, 215, 217. 
Congestion, 72. 
Conjunctiva, 215. 
Connective tissue, 20. 
Consciousness, 201. 
Consumption, 116. 
Contagious diseases, 119. 
Convolutions of brain, 198. 
Convulsions, 26. 
Cooking, 144. 
Cords, vocal, 237, 238. 
Corn, 138. 
Cornea, 215, 217. 



Index. 



2 75 



Corpuscles of blood, 74, 75. 
Lymph, 77-81, 82, 

Coughing, 92. 

Cowpox, 250, 251. 

Cramp, 44. 

Crazy hone, 213. 

Crossing of nerve fibers, 202. 

Crystalline lens, 218, 224, 225, 226. 

Cutaneous sensations, 211. 

Dandruff, 125. 

Deafness and colds, 237. 

Defects of eyesight, 223-230. 

Dermis, 126. 

Desserts, 182. 

Diabetes, 187. 

Diaphragm, 83, 86, 87, 89, 176. 

Diet, mixed, necessity of, 142. 

Proper, 143. 
Diffusion of gases, 106. 
Digestion and circulation, 181. 

In the intestine, 164. 

In the mouth, 146. 

And muscular work, 181. 

And repose, 182. 

In the stomach, 156-161. 

And study, 181. 
Digestive tube, 146. 
Diphtheria, 116. 
Disease germs, 116, 252. 
Dislocations, 14. 
Dropsy, 81. 

Drowning, treatment for, 242-245. 
Drunkards, 255. 
Drunkenness, 256. 
Duodenum, 168. 
Dura mater, 198. 
Dust, 1 1 4- 1 19. 

Ear, 235-237. 

Eating, intemperance in, 183. 

Time of, 183. 
Eddy, body like, 187. 
Eggs, 136. 



Emulsion, 136, 166. 
Energy from food, 188. 
Potential, 91. 

Entire wheat flour, 137. 
Epidermis, 124, 125. 
Epiglottis, 156, 157. 
Equilibrium sense, 236. 
Erysipelas, 116. 
Eustachian tube, 235, 236. 
Excretion, 123-132, 169. 
Exercise and blood flow, 70, 101. 

Forms of, 193. 

For general health, 192-195. 

And respiration, 101. 
Extensors and flexors, 21. 
Eye, 215-221. 
Eyes, care of, 230-232. 
Eyesight, defects of, 223-230. 

Fainting, 206, 241. 

Fans, no. 

Far sight, 226-228. 

Fat, as tissue, 184. 

Fatigue, 205. 

Fats, absorption of, 174, 178. 

As food, 137. 
Fermenting, 115. 
Fibrin, 76. 
Fish, 135. 
Flavors, 234. 

Flexors and extensors, 21. 
Focus, 223. 

Natural, 225. 
Food, I34-I45- 

Amount needed, 183. 

And foodstuffs, 134, 135. 

Need of, 134. 

Object of, 146. 

Preservation of, 121. 

For the sick, 248. 
Football, 194. 
Foot-bath, hot, 73. 
Foul-air shafts, no. 
Freckles, 125. 



276 



Index. 



Fruit, 139. 
Frying, 145. 
Function, defined, 2. 
Furnace, no. 

Ganglions, 67, 68, 201. 
Glands, 169, 170. 

And blood supply, 128. 

Control of, 128, 169. 

Gastric, 159, 160. 

Intestinal, 167, 173. 

Lacrymal, 215. 

Lymphatic, 78, 79. 

Mucous, 154. 

Oil, 124, 126. 

Plan of, 153. 

Salivary, 152-154, 165. 

Sweat, 124, 127. 
Glasses, 223, 227, 228, 229. 
Graham flour, 138. 
Grates, 107, ill. 
Gravity and circulation, 71, 72. 
Grippe, 116. 
Gullet, 147, 156, 157, 158. 

Hair, 124, 126. 

Hammer, 235. 

Heart, 47-49. 

Heart -beat, control of,- 70, 71. 

Rate of, 47, 70. 
Heart-burn, 162. 
Heat, conduction of, 129. 

Convection of, 129. 

Distribution of, 130. 

And exercise, 130. 

In the liver, 102. 

Production of, 100. 

Radiation of, 129. 

Source of, 102. 
Heating, direct, no. 

By hot water, no. 

Indirect, 1 io. 

By steam, 1 10. 
Hemoglobin, 76, 99. 
Hemorrhage, of lungs, 241. 



Of stomach, 241. 
Hiccuping, 92. 
Humor, aqueous, 218. 

Vitreous, 218. 
Hunger, 210. 
Hygiene, defined, 2. 
Hypermetropic eye, 227. 
Hypodermic injections, 82. 

Image, on retina, 218. 

Inflammation, 72. 

Inoculation, 250. 

Intestine, large, 148, 167, 168, 179. 

Small, 147, 164, 168. 
Iris, 215, 217. 

Jenner, Edward, 250. 

Joints, 13. 

Juice, gastric, 159, 160. 

Intestinal, 167. 

Pancreatic, 166. 

Kidneys, 131, 132, 187/ 

Labor, division of, 3. 
Lacrymal secretion, 215. 
Lacteals, 173, 174, 177. 
Larynx, 237, 238. 
Lens, crystalline, 224. 
Levers, 30, 31. 
Liver, 147, 164, 176-178. 
Lockjaw, 44, 116, 251, 252. 
Lungs, 83-88. 

Capacity of, 94. 

Diseases of, 119. 
Lymph, 77-81. 

Capillaries, 77. 

Cavities, 81. 

Spaces, 77. 

Tubes, 77. 

Veins, 175. 
Lymphatic glands, 78, 79, 1 75. 
Lymphatics, 78, 174, 175. 

Mad dog bite, 247. 
Malaria, 116, 121. 
Mastication, 148, 154, 182. 



Index. 



277 



Measles, no. 
Meat, 135. 

Cooking, 144. 
Meningitis, 200. 
Mesentery, 14S. 
Milk, 136. 

Sterilizing, 121. 
Molds, 115. 
Morphine (or Morphia), 253, 254, 255, 

2 S 8. 

Motion, 16, 36. 

Production of, 100. 
Mouth, 147, 14S. 

Breathing through, 95. 
Mucous membrane, 85. 
Mucus, 85, 154. 
Mumps, 116, 154. 
Muscle fiber, of heart, 19. 

Involuntary, 19. 

Plain, 19, 58, 59. 

Striated, 19. 

Voluntary, 19. 
Muscles, 16-26. 

Action of, 17. 

And bones, 28. 

Skeletal, 28. 

Sphincter, 161. 

Structure of, 18, 19. 
Muscular sense, 209. 
Mustard, an emetic, 246. 

Plaster, 72. 
Myopic eye, 227. 

Nails, 127. 
Narcotics, 253-259. 
Nasal passages, 95, 156, 157. 
Near sight, 228-229. 

In children, 228. 
Nerve currents, 208. 
Nerve endings in skin, 211. 
Nerves, auditory, 200. 

Cranial, 199-202. 

Facial, 200. 

Fibers, 39. 



Function of, 39. 

( llosso-pharyngeal, 200. 

Hypo-glossal, 201. 

Olfactory, 199. 

Optic, 199. 

Roots of, 38, 40. 

Sciatic, 18, 37, 43. 

Spinal, 38. 

Structure of, 39. 

Sympathetic, 67, 68. 

Of taste, 233. 

Of tongue, 233. 

Trigeminal, 199. 

Vagus, 71, 200. 
Nitrogen, 97, 135, 143. 
Nucleus, 3, 19, 61. 

Oats, 138. 

Opium, 253, 254, 255, 258. 
Organ, defined, 2. 
Oxidation in the body, 102. 
Oxygen, 97, 98, 99. 
Oxy-hemoglobin, 99. 

Pain, 209, 210. 

Palate, 156, 157. 

Pallor, 69. 

Pancreas, 147, 165, 166. 

Pancreatic juice, 166. 

Papillas, of skin, 125, 126. 

Of tongue, 233. - 
Paralysis, 202. 
Patent medicine, 259. 
Pepsin, 160. 

Peptones, 160, 162, 174, 178. 
Pericardial fluid, 48. 
Pericardium, 48. 
Peristaltic action, 161. 
Perspiration, 123, 124. 
Pharynx, 156. 
Physiology defined, 2. 
Pia mater, 198. 
Pigment, in skin, 125. 
Plants, source of food, 190. 



278 



Index. 



Plasma, 74, 75. 
Pleura, 86. 
Pleurisy, 86. 
Pneumonia, 87, 257. 
Poison ivy, 247. 
Poisons and antidotes, 246. 
Pollen, 115. 

Portal circulation, 175, 176. 
Vein, 165, 175, 176, 177. 
Potatoes, 139. 
Potential energy, 91. 
Presbyopia, 226. 
Pressure sense, 212. 
Proteids, 135. 
Protoplasm, 3. 
Ptyalin, 154. 
Puff balls, 115. 
Pulse, 47. 

Pupil of eye, 215, 217. 
Putrefaction, 121. 
Pylorus, 159, 161. 

Rectum, 167, 168. 

Reflex action, 41-43. 

Rennet, 161. 

Rennin, 161. 

Respiration, artificial, 242-245. 

Control of, 95. 

Forced, 92. 

Movements of, 89-91. 

Organs of, 83. 

Rate of, 92. 
Retina, 216, 217, 218. 
Rice, 138. 
Rickets, 14. 
Roasting, 144. 
Roots of nerves, 38, 40. 
Running, 33. 

Rye, 138. 

Sacrum, 10. 
Saliva, 152-154. 
Salt, 142. 
Scarlatina, 116. 



Sclerotic coat, 215, 216, 225. 
Scrofula, 79, 251. 
Scurvy, 139. 
Secretion, 169. 

Lacrymal, 215. 
Semicircular canals, 235, 236. 
Sensations, cutaneous, 211. 

General, 208. 

Special, 208. 
Sense of equilibrium, 236. 

Muscular, 209. 

Of pressure, 212. 

Of temperature, 213. 
Serous cavities, 81. 
Serum, 76, 77. 
Sick, care of, 247-249. 
Sight, sense of, 215-221. 
Skin, absorption by, 131. 

Color of, 125. 

Grafting, 131. 

Nerve endings in, 211. 

Protection by, 131. 

Structure of, 124. 
Sleeplessness, 205. 
Slippers, 112. 
Smallpox, 116, 250, 251. 
Smell, 234. 
Snake bites, 247. 
Sneezing, 92, 249. 
Sniffing, 234. 
Solar plexus, 68. 
Sound, 236. 
Soup making, 144. 

Value of, 181. 
Spinal bulb, 198, 205. 

Cord, 38, 40, 41. 

Nerves, 38. 
Spleen, 82. 
Sprains, 14. 
Standing, 32. 
Starch, 137. 
Sterilizing milk, 121. 

Surgical instruments, 120. 
Stimulants, 253-259. 



Index. 



279 



Stirrup, 235. 

Stomach, 147, 15S-162, 165, 168. 

Stoves, 10S, 109. 

Suffocation in wells, 245. 

Sugar, 137, 174. 

Sunstroke, 242. 

Swallowing, 157, 158. 

Sweat, 123. 

Amount of, 128. 

Composition of, 127. 

Evaporation of, 129. 
Sweeping, 118, 119. 
Swimming, 245. 
Sympathetic nervous system, 67, < 

Tartar, 152. 
Taste, 233, 234. . 
Tea, 253, 255, 259. 
Tear gland, 215. 
Teeth, 149-152. 
Temperature of body, 101. 

Regulation of, 128. 

Sense, 213. 
Tennis, 194. 
Tetanus, 44, 251. 
Thirst, 210. 

Thoracic duct, 78, 175. 
Tissues, defined, 2. 
Tobacco, 257. 
Tongue, 148. 
Touch, 211-213. 
Trachea, 83. 
Trypsin, 166. 
Tuberculosis, 117, 251. 
Tympanic membrane, 235. 
Typhoid fever, 116, 148, 257. 

Urea, 132. 
Urine, 131, 132. 

Vaccination, 250-252.. 
Vaccine virus, 250, 252. 
Vaccinia, 250, 251. 
Valves of heart, 49, 50, 55, 57. 



In lymph tubes, 78. 

In veins, 62, 63. 

In villuses, 173, 174. 
Vegetables, 1 39. 
Vegetarians, 143. 
Veins, 60-65. 

Hepatic, 176, 178. 

Iliac, 53. 

Jugular, 53, 80. 

Portal, 175-177. 

Post-caval, 51, 52, 53, 54, 80. 

Pre-caval, 52, 53, 54, 80. 

Renal, 53. 

Sub-clavian, 52, 53, 80, 175. 
Ventilation, 106, 108, 112, 113. 
Ventricle, 54, 55, 56, 57. 
Vertebra, 5—1 1. 
Vesicles of lungs, 85. 
Villuses, 173, 174. 
Vitreous humor, 218. 
Vocal cords, 237, 238. 
Voice, 237-239. 
Volition, 201. 

Walking, 33. 

Waste matter, source of, 123. 

Water, 139. 

Drinking, 142. 

Ice, 141. 

Impurities in, 140. 

Rain, 139. 

Well, 140. 
Wheat, 137. 

Flour, 137. 
Whisky, 255, 256, 259. 
Whooping-cough, 116. 
Wind, 107. 
Windows, III. 
Wine, 254, 255, 256, 259. 
Wounds, 240, 247. 

X-rays, 28, 29. 

Yeast, 115. 

Yellow fever, 116, 121. 



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